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 $185.52   11.313%   $206.5079   $206.51   $206.50   $206.50  
  Purchase #2 $91.99   13.581%   $104.4832   $104.48   $104.50   $104.50  
  Purchase #3 $56.92   9.604%   $62.3866   $62.39   $62.40   $62.40  
  Purchase #4 $130.45   3.104%   $134.4992   $134.50   $134.50   $134.50  
  Purchase #5 $132.63   10.520%   $146.5827   $146.58   $146.60   $146.60  
  Purchase #6 $162.82   12.514%   $183.1953   $183.20   $183.20   $183.20  
  Purchase #7 $166.92   12.337%   $187.5129   $187.51   $187.50   $187.50  
  7 purchase totals = $927.25       $1,025.1678   $1,025.17   $1,025.20   $1,025.20