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 $213.89   5.686%   $226.0518   $226.05   $226.05   $226.10  
  Purchase #2 $162.42   9.375%   $177.6469   $177.65   $177.65   $177.60  
  Purchase #3 $146.58   5.165%   $154.1509   $154.15   $154.15   $154.20  
  Purchase #4 $165.93   3.769%   $172.1839   $172.18   $172.20   $172.20  
  Purchase #5 $119.35   3.751%   $123.8268   $123.83   $123.85   $123.80  
  Purchase #6 $47.82   9.496%   $52.361   $52.36   $52.35   $52.40  
  Purchase #7 $250.98   4.729%   $262.8488   $262.85   $262.85   $262.80  
  7 purchase totals = $1,106.97       $1,169.0701   $1,169.07   $1,169.10   $1,169.10