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 $193.95   5.281%   $204.1925   $204.19   $204.20   $204.20  
  Purchase #2 $73.44   7.866%   $79.2168   $79.22   $79.20   $79.20  
  Purchase #3 $10.43   9.118%   $11.381   $11.38   $11.40   $11.40  
  Purchase #4 $153.44   11.502%   $171.0887   $171.09   $171.10   $171.10  
  Purchase #5 $50.58   9.684%   $55.4782   $55.48   $55.50   $55.50  
  Purchase #6 $203.86   6.593%   $217.3005   $217.30   $217.30   $217.30  
  Purchase #7 $210.30   12.462%   $236.5076   $236.51   $236.50   $236.50  
  7 purchase totals = $896.00       $975.1653   $975.17   $975.20   $975.20