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 $41.32   11.207%   $45.9507   $45.95   $45.95   $46.00  
  Purchase #2 $149.56   7.343%   $160.5422   $160.54   $160.55   $160.50  
  Purchase #3 $124.96   9.845%   $137.2623   $137.26   $137.25   $137.30  
  Purchase #4 $120.43   11.162%   $133.8724   $133.87   $133.85   $133.90  
  Purchase #5 $74.25   9.321%   $81.1708   $81.17   $81.15   $81.20  
  Purchase #6 $54.58   10.720%   $60.431   $60.43   $60.45   $60.40  
  Purchase #7 $71.96   6.378%   $76.5496   $76.55   $76.55   $76.50  
  7 purchase totals = $637.06       $695.7790   $695.77   $695.75   $695.80