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 $225.67   7.164%   $241.837   $241.84   $241.85   $241.80  
  Purchase #2 $195.51   9.276%   $213.6455   $213.65   $213.65   $213.60  
  Purchase #3 $73.85   11.164%   $82.0946   $82.09   $82.10   $82.10  
  Purchase #4 $101.47   7.316%   $108.8935   $108.89   $108.90   $108.90  
  Purchase #5 $214.96   7.304%   $230.6607   $230.66   $230.65   $230.70  
  Purchase #6 $35.99   11.584%   $40.1591   $40.16   $40.15   $40.20  
  Purchase #7 $240.52   4.129%   $250.4511   $250.45   $250.45   $250.50  
  7 purchase totals = $1,087.97       $1,167.7415   $1,167.74   $1,167.75   $1,167.80