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 $95.66   9.365%   $104.6186   $104.62   $104.60   $104.60  
  Purchase #2 $173.57   7.432%   $186.4697   $186.47   $186.45   $186.50  
  Purchase #3 $101.32   11.371%   $112.8411   $112.84   $112.85   $112.80  
  Purchase #4 $208.26   7.165%   $223.1818   $223.18   $223.20   $223.20  
  Purchase #5 $59.60   4.215%   $62.1121   $62.11   $62.10   $62.10  
  Purchase #6 $141.91   9.424%   $155.2836   $155.28   $155.30   $155.30  
  Purchase #7 $175.35   3.743%   $181.9134   $181.91   $181.90   $181.90  
  7 purchase totals = $955.67       $1,026.4203   $1,026.41   $1,026.40   $1,026.40