Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $206.95   9.520%   $226.6516   $226.65   $226.65   $226.70  
  Purchase #2 $161.53   9.330%   $176.6007   $176.60   $176.60   $176.60  
  Purchase #3 $164.62   10.136%   $181.3059   $181.31   $181.30   $181.30  
  Purchase #4 $118.45   11.729%   $132.343   $132.34   $132.35   $132.30  
  Purchase #5 $222.67   9.417%   $243.6388   $243.64   $243.65   $243.60  
  Purchase #6 $201.42   11.169%   $223.9166   $223.92   $223.90   $223.90  
  Purchase #7 $98.41   9.411%   $107.6714   $107.67   $107.65   $107.70  
  7 purchase totals = $1,174.05       $1,292.1280   $1,292.13   $1,292.10   $1,292.10