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 $105.55   7.307%   $113.2625   $113.26   $113.25   $113.30  
  Purchase #2 $91.93   3.693%   $95.325   $95.33   $95.35   $95.30  
  Purchase #3 $79.82   10.816%   $88.4533   $88.45   $88.45   $88.50  
  Purchase #4 $248.84   4.833%   $260.8664   $260.87   $260.85   $260.90  
  Purchase #5 $91.88   5.491%   $96.9251   $96.93   $96.95   $96.90  
  Purchase #6 $216.60   3.518%   $224.22   $224.22   $224.20   $224.20  
  Purchase #7 $15.93   4.116%   $16.5857   $16.59   $16.60   $16.60  
  7 purchase totals = $850.55       $895.6380   $895.65   $895.65   $895.70