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 $87.52   9.686%   $95.9972   $96.00   $96.00   $96.00  
  Purchase #2 $93.38   13.459%   $105.948   $105.95   $105.95   $105.90  
  Purchase #3 $244.25   9.241%   $266.8211   $266.82   $266.80   $266.80  
  Purchase #4 $241.30   11.535%   $269.134   $269.13   $269.15   $269.10  
  Purchase #5 $209.40   11.670%   $233.837   $233.84   $233.85   $233.80  
  Purchase #6 $192.36   12.860%   $217.0975   $217.10   $217.10   $217.10  
  Purchase #7 $74.32   5.643%   $78.5139   $78.51   $78.50   $78.50  
  7 purchase totals = $1,142.53       $1,267.3487   $1,267.35   $1,267.35   $1,267.20