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 $147.38   4.525%   $154.0489   $154.05   $154.05   $154.00  
  Purchase #2 $71.78   10.116%   $79.0413   $79.04   $79.05   $79.00  
  Purchase #3 $26.75   3.871%   $27.7855   $27.79   $27.80   $27.80  
  Purchase #4 $93.84   4.110%   $97.6968   $97.70   $97.70   $97.70  
  Purchase #5 $232.98   9.375%   $254.8219   $254.82   $254.80   $254.80  
  Purchase #6 $194.73   3.659%   $201.8552   $201.86   $201.85   $201.90  
  Purchase #7 $194.71   7.114%   $208.5617   $208.56   $208.55   $208.60  
  7 purchase totals = $962.17       $1,023.8113   $1,023.82   $1,023.80   $1,023.80