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 $84.28   12.534%   $94.8437   $94.84   $94.85   $94.80  
  Purchase #2 $177.71   5.598%   $187.6582   $187.66   $187.65   $187.70  
  Purchase #3 $238.92   5.398%   $251.8169   $251.82   $251.80   $251.80  
  Purchase #4 $178.50   7.526%   $191.9339   $191.93   $191.95   $191.90  
  Purchase #5 $88.86   7.462%   $95.4907   $95.49   $95.50   $95.50  
  Purchase #6 $152.88   11.420%   $170.3389   $170.34   $170.35   $170.30  
  Purchase #7 $150.38   3.406%   $155.5019   $155.50   $155.50   $155.50  
  7 purchase totals = $1,071.53       $1,147.5842   $1,147.58   $1,147.60   $1,147.50