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 $162.96   7.293%   $174.8447   $174.84   $174.85   $174.80  
  Purchase #2 $86.89   7.413%   $93.3312   $93.33   $93.35   $93.30  
  Purchase #3 $9.44   13.591%   $10.723   $10.72   $10.70   $10.70  
  Purchase #4 $91.46   5.506%   $96.4958   $96.50   $96.50   $96.50  
  Purchase #5 $68.69   8.303%   $74.3933   $74.39   $74.40   $74.40  
  Purchase #6 $228.76   3.857%   $237.5833   $237.58   $237.60   $237.60  
  Purchase #7 $69.84   8.532%   $75.7987   $75.80   $75.80   $75.80  
  7 purchase totals = $718.04       $763.1700   $763.16   $763.20   $763.10