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 $86.25   11.626%   $96.2774   $96.28   $96.30   $96.30  
  Purchase #2 $146.52   7.342%   $157.2775   $157.28   $157.30   $157.30  
  Purchase #3 $39.78   5.199%   $41.8482   $41.85   $41.85   $41.80  
  Purchase #4 $200.29   3.846%   $207.9932   $207.99   $208.00   $208.00  
  Purchase #5 $75.83   6.344%   $80.6407   $80.64   $80.65   $80.60  
  Purchase #6 $56.66   13.579%   $64.3539   $64.35   $64.35   $64.40  
  Purchase #7 $106.27   10.625%   $117.5612   $117.56   $117.55   $117.60  
  7 purchase totals = $711.60       $765.9521   $765.95   $766.00   $766.00