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 $54.49   13.841%   $62.032   $62.03   $62.05   $62.00  
  Purchase #2 $219.27   12.363%   $246.3784   $246.38   $246.40   $246.40  
  Purchase #3 $134.43   11.636%   $150.0723   $150.07   $150.05   $150.10  
  Purchase #4 $48.57   3.711%   $50.3724   $50.37   $50.35   $50.40  
  Purchase #5 $26.80   6.319%   $28.4935   $28.49   $28.50   $28.50  
  Purchase #6 $31.93   3.427%   $33.0242   $33.02   $33.00   $33.00  
  Purchase #7 $231.68   13.867%   $263.8071   $263.81   $263.80   $263.80  
  7 purchase totals = $747.17       $834.1799   $834.17   $834.15   $834.20