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 $64.96   6.141%   $68.9492   $68.95   $68.95   $68.90  
  Purchase #2 $236.84   10.115%   $260.7964   $260.80   $260.80   $260.80  
  Purchase #3 $63.94   11.850%   $71.5169   $71.52   $71.50   $71.50  
  Purchase #4 $138.71   9.384%   $151.7265   $151.73   $151.75   $151.70  
  Purchase #5 $49.56   4.498%   $51.7892   $51.79   $51.80   $51.80  
  Purchase #6 $245.40   9.693%   $269.1866   $269.19   $269.20   $269.20  
  Purchase #7 $69.26   6.172%   $73.5347   $73.53   $73.55   $73.50  
  7 purchase totals = $868.67       $947.4995   $947.51   $947.55   $947.40