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 $95.81   6.420%   $101.961   $101.96   $101.95   $102.00  
  Purchase #2 $110.87   11.263%   $123.3573   $123.36   $123.35   $123.40  
  Purchase #3 $63.31   5.791%   $66.9763   $66.98   $67.00   $67.00  
  Purchase #4 $29.72   6.727%   $31.7193   $31.72   $31.70   $31.70  
  Purchase #5 $153.89   6.286%   $163.5635   $163.56   $163.55   $163.60  
  Purchase #6 $194.39   8.694%   $211.2903   $211.29   $211.30   $211.30  
  Purchase #7 $118.83   6.198%   $126.1951   $126.20   $126.20   $126.20  
  7 purchase totals = $766.82       $825.0628   $825.07   $825.05   $825.20