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 $60.39   7.578%   $64.9664   $64.97   $64.95   $65.00  
  Purchase #2 $63.78   11.351%   $71.0197   $71.02   $71.00   $71.00  
  Purchase #3 $197.59   4.106%   $205.703   $205.70   $205.70   $205.70  
  Purchase #4 $140.47   13.354%   $159.2284   $159.23   $159.25   $159.20  
  Purchase #5 $166.66   11.404%   $185.6659   $185.67   $185.65   $185.70  
  Purchase #6 $88.35   7.691%   $95.145   $95.15   $95.15   $95.10  
  Purchase #7 $177.84   9.847%   $195.3519   $195.35   $195.35   $195.40  
  7 purchase totals = $895.08       $977.0803   $977.09   $977.05   $977.10