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 $185.95   5.363%   $195.9225   $195.92   $195.90   $195.90  
  Purchase #2 $223.81   4.194%   $233.1966   $233.20   $233.20   $233.20  
  Purchase #3 $70.32   8.752%   $76.4744   $76.47   $76.45   $76.50  
  Purchase #4 $35.96   9.336%   $39.3172   $39.32   $39.30   $39.30  
  Purchase #5 $225.71   3.121%   $232.7544   $232.75   $232.75   $232.80  
  Purchase #6 $113.50   13.111%   $128.381   $128.38   $128.40   $128.40  
  Purchase #7 $43.74   9.292%   $47.8043   $47.80   $47.80   $47.80  
  7 purchase totals = $898.99       $953.8504   $953.84   $953.80   $953.90