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 $95.55   6.748%   $101.9977   $102.00   $102.00   $102.00  
  Purchase #2 $250.96   4.140%   $261.3497   $261.35   $261.35   $261.30  
  Purchase #3 $220.85   10.804%   $244.7106   $244.71   $244.70   $244.70  
  Purchase #4 $220.89   11.656%   $246.6369   $246.64   $246.65   $246.60  
  Purchase #5 $216.50   6.809%   $231.2415   $231.24   $231.25   $231.20  
  Purchase #6 $98.65   13.776%   $112.24   $112.24   $112.25   $112.20  
  Purchase #7 $157.47   12.847%   $177.7002   $177.70   $177.70   $177.70  
  7 purchase totals = $1,260.87       $1,375.8766   $1,375.88   $1,375.90   $1,375.70