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 $57.37   6.235%   $60.947   $60.95   $60.95   $60.90  
  Purchase #2 $146.82   12.703%   $165.4705   $165.47   $165.45   $165.50  
  Purchase #3 $205.53   11.384%   $228.9275   $228.93   $228.95   $228.90  
  Purchase #4 $20.52   8.419%   $22.2476   $22.25   $22.25   $22.20  
  Purchase #5 $151.45   8.496%   $164.3172   $164.32   $164.30   $164.30  
  Purchase #6 $29.62   11.616%   $33.0607   $33.06   $33.05   $33.10  
  Purchase #7 $221.58   6.743%   $236.5211   $236.52   $236.50   $236.50  
  7 purchase totals = $832.89       $911.4916   $911.50   $911.45   $911.40