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 $95.60   11.678%   $106.7642   $106.76   $106.75   $106.80  
  Purchase #2 $226.34   7.677%   $243.7161   $243.72   $243.70   $243.70  
  Purchase #3 $202.45   5.417%   $213.4167   $213.42   $213.40   $213.40  
  Purchase #4 $87.49   6.686%   $93.3396   $93.34   $93.35   $93.30  
  Purchase #5 $204.33   6.775%   $218.1734   $218.17   $218.15   $218.20  
  Purchase #6 $158.39   10.403%   $174.8673   $174.87   $174.85   $174.90  
  Purchase #7 $194.65   7.535%   $209.3169   $209.32   $209.30   $209.30  
  7 purchase totals = $1,169.25       $1,259.5942   $1,259.60   $1,259.50   $1,259.60