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 $218.83   6.134%   $232.253   $232.25   $232.25   $232.30  
  Purchase #2 $229.62   7.742%   $247.3972   $247.40   $247.40   $247.40  
  Purchase #3 $43.59   7.251%   $46.7507   $46.75   $46.75   $46.80  
  Purchase #4 $225.64   5.609%   $238.2961   $238.30   $238.30   $238.30  
  Purchase #5 $239.73   6.446%   $255.183   $255.18   $255.20   $255.20  
  Purchase #6 $139.59   7.623%   $150.2309   $150.23   $150.25   $150.20  
  Purchase #7 $184.90   6.732%   $197.3475   $197.35   $197.35   $197.30  
  7 purchase totals = $1,281.90       $1,367.4584   $1,367.46   $1,367.50   $1,367.50