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 $59.66   4.378%   $62.2719   $62.27   $62.25   $62.30  
  Purchase #2 $151.90   9.775%   $166.7482   $166.75   $166.75   $166.70  
  Purchase #3 $104.74   11.287%   $116.562   $116.56   $116.55   $116.60  
  Purchase #4 $81.45   9.306%   $89.0297   $89.03   $89.05   $89.00  
  Purchase #5 $214.36   6.390%   $228.0576   $228.06   $228.05   $228.10  
  Purchase #6 $243.39   8.352%   $263.7179   $263.72   $263.70   $263.70  
  Purchase #7 $25.76   13.413%   $29.2152   $29.22   $29.20   $29.20  
  7 purchase totals = $881.26       $955.6025   $955.61   $955.55   $955.60