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 $60.67   7.465%   $65.199   $65.20   $65.20   $65.20  
  Purchase #2 $53.76   4.312%   $56.0781   $56.08   $56.10   $56.10  
  Purchase #3 $20.50   11.799%   $22.9188   $22.92   $22.90   $22.90  
  Purchase #4 $33.78   5.430%   $35.6143   $35.61   $35.60   $35.60  
  Purchase #5 $175.49   11.639%   $195.9153   $195.92   $195.90   $195.90  
  Purchase #6 $147.39   9.161%   $160.8924   $160.89   $160.90   $160.90  
  Purchase #7 $210.76   7.185%   $225.9031   $225.90   $225.90   $225.90  
  7 purchase totals = $702.35       $762.5210   $762.52   $762.50   $762.50