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 $109.68   9.167%   $119.7344   $119.73   $119.75   $119.70  
  Purchase #2 $147.40   12.117%   $165.2605   $165.26   $165.25   $165.30  
  Purchase #3 $244.39   9.295%   $267.1061   $267.11   $267.10   $267.10  
  Purchase #4 $99.75   8.829%   $108.5569   $108.56   $108.55   $108.60  
  Purchase #5 $165.73   6.344%   $176.2439   $176.24   $176.25   $176.20  
  Purchase #6 $149.69   13.614%   $170.0688   $170.07   $170.05   $170.10  
  Purchase #7 $85.55   3.533%   $88.5725   $88.57   $88.55   $88.60  
  7 purchase totals = $1,002.19       $1,095.5431   $1,095.54   $1,095.50   $1,095.60