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 $59.85   13.592%   $67.9848   $67.98   $68.00   $68.00  
  Purchase #2 $136.83   10.484%   $151.1753   $151.18   $151.20   $151.20  
  Purchase #3 $216.51   8.607%   $235.145   $235.15   $235.15   $235.10  
  Purchase #4 $35.80   13.811%   $40.7443   $40.74   $40.75   $40.70  
  Purchase #5 $156.51   12.349%   $175.8374   $175.84   $175.85   $175.80  
  Purchase #6 $101.42   6.135%   $107.6421   $107.64   $107.65   $107.60  
  Purchase #7 $110.93   5.216%   $116.7161   $116.72   $116.70   $116.70  
  7 purchase totals = $817.85       $895.2450   $895.25   $895.30   $895.10