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 $87.54   5.649%   $92.4851   $92.49   $92.50   $92.50  
  Purchase #2 $195.28   11.633%   $217.9969   $218.00   $218.00   $218.00  
  Purchase #3 $112.90   11.255%   $125.6069   $125.61   $125.60   $125.60  
  Purchase #4 $213.82   13.700%   $243.1133   $243.11   $243.10   $243.10  
  Purchase #5 $67.78   12.448%   $76.2173   $76.22   $76.20   $76.20  
  Purchase #6 $191.32   6.440%   $203.641   $203.64   $203.65   $203.60  
  Purchase #7 $209.98   12.160%   $235.5136   $235.51   $235.50   $235.50  
  7 purchase totals = $1,078.62       $1,194.5741   $1,194.58   $1,194.55   $1,194.50