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 $168.97   3.546%   $174.9617   $174.96   $174.95   $175.00  
  Purchase #2 $19.56   11.594%   $21.8278   $21.83   $21.85   $21.80  
  Purchase #3 $247.95   11.316%   $276.008   $276.01   $276.00   $276.00  
  Purchase #4 $230.98   6.746%   $246.5619   $246.56   $246.55   $246.60  
  Purchase #5 $104.53   3.462%   $108.1488   $108.15   $108.15   $108.10  
  Purchase #6 $60.33   4.253%   $62.8958   $62.90   $62.90   $62.90  
  Purchase #7 $174.60   4.582%   $182.6002   $182.60   $182.60   $182.60  
  7 purchase totals = $1,006.92       $1,073.0042   $1,073.01   $1,073.00   $1,073.00