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 $173.97   11.698%   $194.321   $194.32   $194.30   $194.30  
  Purchase #2 $145.86   11.507%   $162.6441   $162.64   $162.65   $162.60  
  Purchase #3 $176.39   10.676%   $195.2214   $195.22   $195.20   $195.20  
  Purchase #4 $223.92   13.517%   $254.1873   $254.19   $254.20   $254.20  
  Purchase #5 $92.46   4.490%   $96.6115   $96.61   $96.60   $96.60  
  Purchase #6 $154.28   13.561%   $175.2019   $175.20   $175.20   $175.20  
  Purchase #7 $69.31   9.715%   $76.0435   $76.04   $76.05   $76.00  
  7 purchase totals = $1,036.19       $1,154.2307   $1,154.22   $1,154.20   $1,154.10