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 $56.49   11.459%   $62.9632   $62.96   $62.95   $63.00  
  Purchase #2 $51.32   5.445%   $54.1144   $54.11   $54.10   $54.10  
  Purchase #3 $118.37   9.148%   $129.1985   $129.20   $129.20   $129.20  
  Purchase #4 $74.40   9.375%   $81.375   $81.38   $81.40   $81.40  
  Purchase #5 $147.80   9.138%   $161.306   $161.31   $161.30   $161.30  
  Purchase #6 $185.81   12.871%   $209.7256   $209.73   $209.75   $209.70  
  Purchase #7 $200.95   4.490%   $209.9727   $209.97   $209.95   $210.00  
  7 purchase totals = $835.14       $908.6554   $908.66   $908.65   $908.70