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 $85.89   7.319%   $92.1763   $92.18   $92.20   $92.20  
  Purchase #2 $193.72   9.383%   $211.8967   $211.90   $211.90   $211.90  
  Purchase #3 $131.45   13.199%   $148.8001   $148.80   $148.80   $148.80  
  Purchase #4 $53.60   9.742%   $58.8217   $58.82   $58.80   $58.80  
  Purchase #5 $42.25   9.563%   $46.2904   $46.29   $46.30   $46.30  
  Purchase #6 $162.76   5.349%   $171.466   $171.47   $171.45   $171.50  
  Purchase #7 $188.81   8.310%   $204.5001   $204.50   $204.50   $204.50  
  7 purchase totals = $858.48       $933.9513   $933.96   $933.95   $934.00