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 $134.98   9.366%   $147.6222   $147.62   $147.60   $147.60  
  Purchase #2 $217.61   5.853%   $230.3467   $230.35   $230.35   $230.30  
  Purchase #3 $49.89   8.460%   $54.1107   $54.11   $54.10   $54.10  
  Purchase #4 $87.88   10.621%   $97.2137   $97.21   $97.20   $97.20  
  Purchase #5 $203.88   6.159%   $216.437   $216.44   $216.45   $216.40  
  Purchase #6 $99.73   3.347%   $103.068   $103.07   $103.05   $103.10  
  Purchase #7 $104.53   7.557%   $112.4293   $112.43   $112.45   $112.40  
  7 purchase totals = $898.50       $961.2276   $961.23   $961.20   $961.10