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 $62.27   10.725%   $68.9485   $68.95   $68.95   $68.90  
  Purchase #2 $157.83   8.501%   $171.2471   $171.25   $171.25   $171.20  
  Purchase #3 $12.37   5.834%   $13.0917   $13.09   $13.10   $13.10  
  Purchase #4 $108.93   11.251%   $121.1857   $121.19   $121.20   $121.20  
  Purchase #5 $236.40   9.111%   $257.9384   $257.94   $257.95   $257.90  
  Purchase #6 $72.28   9.266%   $78.9775   $78.98   $79.00   $79.00  
  Purchase #7 $108.52   13.213%   $122.8587   $122.86   $122.85   $122.90  
  7 purchase totals = $758.60       $834.2476   $834.26   $834.30   $834.20