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 $60.63   3.849%   $62.9636   $62.96   $62.95   $63.00  
  Purchase #2 $167.84   4.258%   $174.9866   $174.99   $175.00   $175.00  
  Purchase #3 $235.30   7.650%   $253.3005   $253.30   $253.30   $253.30  
  Purchase #4 $120.96   13.476%   $137.2606   $137.26   $137.25   $137.30  
  Purchase #5 $122.79   10.635%   $135.8487   $135.85   $135.85   $135.80  
  Purchase #6 $59.85   3.735%   $62.0854   $62.09   $62.10   $62.10  
  Purchase #7 $150.85   12.356%   $169.489   $169.49   $169.50   $169.50  
  7 purchase totals = $918.22       $995.9344   $995.94   $995.95   $996.00