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 $119.44   5.530%   $126.045   $126.05   $126.05   $126.00  
  Purchase #2 $191.27   7.618%   $205.8409   $205.84   $205.85   $205.80  
  Purchase #3 $70.87   13.202%   $80.2263   $80.23   $80.25   $80.20  
  Purchase #4 $163.77   3.516%   $169.5282   $169.53   $169.55   $169.50  
  Purchase #5 $91.87   13.530%   $104.3   $104.30   $104.30   $104.30  
  Purchase #6 $194.47   4.648%   $203.509   $203.51   $203.50   $203.50  
  Purchase #7 $31.79   4.472%   $33.2116   $33.21   $33.20   $33.20  
  7 purchase totals = $863.48       $922.6610   $922.67   $922.70   $922.50