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 $201.63   7.747%   $217.2503   $217.25   $217.25   $217.30  
  Purchase #2 $177.84   9.485%   $194.7081   $194.71   $194.70   $194.70  
  Purchase #3 $44.73   4.340%   $46.6713   $46.67   $46.65   $46.70  
  Purchase #4 $220.27   5.522%   $232.4333   $232.43   $232.45   $232.40  
  Purchase #5 $33.77   7.307%   $36.2376   $36.24   $36.25   $36.20  
  Purchase #6 $203.68   10.468%   $225.0012   $225.00   $225.00   $225.00  
  Purchase #7 $93.45   7.764%   $100.7055   $100.71   $100.70   $100.70  
  7 purchase totals = $975.37       $1,053.0073   $1,053.01   $1,053.00   $1,053.00