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 $54.84   12.503%   $61.6966   $61.70   $61.70   $61.70  
  Purchase #2 $45.35   4.309%   $47.3041   $47.30   $47.30   $47.30  
  Purchase #3 $56.43   4.475%   $58.9552   $58.96   $58.95   $59.00  
  Purchase #4 $92.62   5.623%   $97.828   $97.83   $97.85   $97.80  
  Purchase #5 $79.86   9.207%   $87.2127   $87.21   $87.20   $87.20  
  Purchase #6 $17.55   5.625%   $18.5372   $18.54   $18.55   $18.50  
  Purchase #7 $69.47   10.465%   $76.74   $76.74   $76.75   $76.70  
  7 purchase totals = $416.12       $448.2738   $448.28   $448.30   $448.20