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 $112.68   11.796%   $125.9717   $125.97   $125.95   $126.00  
  Purchase #2 $19.38   13.763%   $22.0473   $22.05   $22.05   $22.00  
  Purchase #3 $211.52   13.873%   $240.8642   $240.86   $240.85   $240.90  
  Purchase #4 $233.93   12.790%   $263.8496   $263.85   $263.85   $263.80  
  Purchase #5 $146.74   4.743%   $153.6999   $153.70   $153.70   $153.70  
  Purchase #6 $80.44   13.368%   $91.1932   $91.19   $91.20   $91.20  
  Purchase #7 $109.37   6.804%   $116.8115   $116.81   $116.80   $116.80  
  7 purchase totals = $914.06       $1,014.4374   $1,014.43   $1,014.40   $1,014.40