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 $119.59   3.362%   $123.6106   $123.61   $123.60   $123.60  
  Purchase #2 $26.50   10.567%   $29.3003   $29.30   $29.30   $29.30  
  Purchase #3 $146.80   4.640%   $153.6115   $153.61   $153.60   $153.60  
  Purchase #4 $198.87   13.801%   $226.316   $226.32   $226.30   $226.30  
  Purchase #5 $243.39   7.496%   $261.6345   $261.63   $261.65   $261.60  
  Purchase #6 $150.91   5.614%   $159.3821   $159.38   $159.40   $159.40  
  Purchase #7 $143.84   9.204%   $157.079   $157.08   $157.10   $157.10  
  7 purchase totals = $1,029.90       $1,110.9340   $1,110.93   $1,110.95   $1,110.90