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 $47.37   6.778%   $50.5807   $50.58   $50.60   $50.60  
  Purchase #2 $173.42   12.630%   $195.3229   $195.32   $195.30   $195.30  
  Purchase #3 $171.90   10.310%   $189.6229   $189.62   $189.60   $189.60  
  Purchase #4 $109.49   5.424%   $115.4287   $115.43   $115.45   $115.40  
  Purchase #5 $68.65   5.302%   $72.2898   $72.29   $72.30   $72.30  
  Purchase #6 $165.65   9.218%   $180.9196   $180.92   $180.90   $180.90  
  Purchase #7 $145.44   8.799%   $158.2373   $158.24   $158.25   $158.20  
  7 purchase totals = $881.92       $962.4019   $962.40   $962.40   $962.30