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 $244.49   9.237%   $267.0735   $267.07   $267.05   $267.10  
  Purchase #2 $184.96   10.619%   $204.6009   $204.60   $204.60   $204.60  
  Purchase #3 $58.51   3.195%   $60.3794   $60.38   $60.40   $60.40  
  Purchase #4 $94.82   7.449%   $101.8831   $101.88   $101.90   $101.90  
  Purchase #5 $207.91   5.580%   $219.5114   $219.51   $219.50   $219.50  
  Purchase #6 $35.86   5.762%   $37.9263   $37.93   $37.95   $37.90  
  Purchase #7 $244.39   10.584%   $270.2562   $270.26   $270.25   $270.30  
  7 purchase totals = $1,070.94       $1,161.6308   $1,161.63   $1,161.65   $1,161.70