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 $195.66   4.527%   $204.5175   $204.52   $204.50   $204.50  
  Purchase #2 $73.36   11.785%   $82.0055   $82.01   $82.00   $82.00  
  Purchase #3 $111.85   9.389%   $122.3516   $122.35   $122.35   $122.40  
  Purchase #4 $87.27   6.277%   $92.7479   $92.75   $92.75   $92.70  
  Purchase #5 $128.51   4.653%   $134.4896   $134.49   $134.50   $134.50  
  Purchase #6 $101.77   11.232%   $113.2008   $113.20   $113.20   $113.20  
  Purchase #7 $105.80   11.533%   $118.0019   $118.00   $118.00   $118.00  
  7 purchase totals = $804.22       $867.3148   $867.32   $867.30   $867.30