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 $53.48   13.489%   $60.6939   $60.69   $60.70   $60.70  
  Purchase #2 $187.72   4.112%   $195.439   $195.44   $195.45   $195.40  
  Purchase #3 $69.44   3.762%   $72.0523   $72.05   $72.05   $72.10  
  Purchase #4 $250.66   8.646%   $272.3321   $272.33   $272.35   $272.30  
  Purchase #5 $209.75   6.815%   $224.0445   $224.04   $224.05   $224.00  
  Purchase #6 $204.63   11.386%   $227.9292   $227.93   $227.95   $227.90  
  Purchase #7 $64.29   11.579%   $71.7341   $71.73   $71.75   $71.70  
  7 purchase totals = $1,039.97       $1,124.2251   $1,124.21   $1,124.30   $1,124.10