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 $216.52   8.786%   $235.5434   $235.54   $235.55   $235.50  
  Purchase #2 $193.49   9.237%   $211.3627   $211.36   $211.35   $211.40  
  Purchase #3 $115.93   9.325%   $126.7405   $126.74   $126.75   $126.70  
  Purchase #4 $242.54   6.189%   $257.5508   $257.55   $257.55   $257.60  
  Purchase #5 $238.67   6.208%   $253.4866   $253.49   $253.50   $253.50  
  Purchase #6 $150.57   11.473%   $167.8449   $167.84   $167.85   $167.80  
  Purchase #7 $226.26   10.258%   $249.4698   $249.47   $249.45   $249.50  
  7 purchase totals = $1,383.98       $1,501.9987   $1,501.99   $1,502.00   $1,502.00