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 $86.94   7.820%   $93.7387   $93.74   $93.75   $93.70  
  Purchase #2 $224.94   5.184%   $236.6009   $236.60   $236.60   $236.60  
  Purchase #3 $92.91   5.498%   $98.0182   $98.02   $98.00   $98.00  
  Purchase #4 $37.37   7.868%   $40.3103   $40.31   $40.30   $40.30  
  Purchase #5 $237.85   12.588%   $267.7906   $267.79   $267.80   $267.80  
  Purchase #6 $126.92   7.322%   $136.2131   $136.21   $136.20   $136.20  
  Purchase #7 $169.72   9.477%   $185.8044   $185.80   $185.80   $185.80  
  7 purchase totals = $976.65       $1,058.4762   $1,058.47   $1,058.45   $1,058.40