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 $86.97   8.869%   $94.6834   $94.68   $94.70   $94.70  
  Purchase #2 $194.90   9.663%   $213.7332   $213.73   $213.75   $213.70  
  Purchase #3 $105.95   12.112%   $118.7827   $118.78   $118.80   $118.80  
  Purchase #4 $140.38   9.218%   $153.3202   $153.32   $153.30   $153.30  
  Purchase #5 $194.79   11.448%   $217.0896   $217.09   $217.10   $217.10  
  Purchase #6 $197.62   7.762%   $212.9593   $212.96   $212.95   $213.00  
  Purchase #7 $5.90   5.851%   $6.2452   $6.25   $6.25   $6.20  
  7 purchase totals = $926.51       $1,016.8136   $1,016.81   $1,016.85   $1,016.80