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 $183.33   6.526%   $195.2941   $195.29   $195.30   $195.30  
  Purchase #2 $187.59   8.734%   $203.9741   $203.97   $203.95   $204.00  
  Purchase #3 $68.68   4.400%   $71.7019   $71.70   $71.70   $71.70  
  Purchase #4 $189.38   12.727%   $213.4824   $213.48   $213.50   $213.50  
  Purchase #5 $97.67   4.373%   $101.9411   $101.94   $101.95   $101.90  
  Purchase #6 $148.66   8.369%   $161.1014   $161.10   $161.10   $161.10  
  Purchase #7 $62.58   3.852%   $64.9906   $64.99   $65.00   $65.00  
  7 purchase totals = $937.89       $1,012.4856   $1,012.47   $1,012.50   $1,012.50