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 $116.26   7.722%   $125.2376   $125.24   $125.25   $125.20  
  Purchase #2 $65.52   13.809%   $74.5677   $74.57   $74.55   $74.60  
  Purchase #3 $119.47   4.173%   $124.4555   $124.46   $124.45   $124.50  
  Purchase #4 $198.61   13.291%   $225.0073   $225.01   $225.00   $225.00  
  Purchase #5 $162.62   9.523%   $178.1063   $178.11   $178.10   $178.10  
  Purchase #6 $145.45   11.557%   $162.2597   $162.26   $162.25   $162.30  
  Purchase #7 $54.97   5.754%   $58.133   $58.13   $58.15   $58.10  
  7 purchase totals = $862.90       $947.7671   $947.78   $947.75   $947.80