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 $187.54   4.254%   $195.518   $195.52   $195.50   $195.50  
  Purchase #2 $46.58   5.668%   $49.2202   $49.22   $49.20   $49.20  
  Purchase #3 $92.71   4.502%   $96.8838   $96.88   $96.90   $96.90  
  Purchase #4 $127.30   7.696%   $137.097   $137.10   $137.10   $137.10  
  Purchase #5 $55.73   13.643%   $63.3332   $63.33   $63.35   $63.30  
  Purchase #6 $85.77   12.171%   $96.2091   $96.21   $96.20   $96.20  
  Purchase #7 $57.43   6.246%   $61.0171   $61.02   $61.00   $61.00  
  7 purchase totals = $653.06       $699.2784   $699.28   $699.25   $699.20