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 $184.79   8.248%   $200.0315   $200.03   $200.05   $200.00  
  Purchase #2 $91.38   7.573%   $98.3002   $98.30   $98.30   $98.30  
  Purchase #3 $234.78   4.564%   $245.4954   $245.50   $245.50   $245.50  
  Purchase #4 $151.53   12.148%   $169.9379   $169.94   $169.95   $169.90  
  Purchase #5 $54.78   13.588%   $62.2235   $62.22   $62.20   $62.20  
  Purchase #6 $173.75   12.425%   $195.3384   $195.34   $195.35   $195.30  
  Purchase #7 $70.45   9.233%   $76.9546   $76.95   $76.95   $77.00  
  7 purchase totals = $961.46       $1,048.2815   $1,048.28   $1,048.30   $1,048.20