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 $162.54   3.198%   $167.738   $167.74   $167.75   $167.70  
  Purchase #2 $226.86   6.519%   $241.649   $241.65   $241.65   $241.60  
  Purchase #3 $239.54   13.809%   $272.6181   $272.62   $272.60   $272.60  
  Purchase #4 $243.44   8.176%   $263.3437   $263.34   $263.35   $263.30  
  Purchase #5 $104.64   7.666%   $112.6617   $112.66   $112.65   $112.70  
  Purchase #6 $207.94   11.387%   $231.6181   $231.62   $231.60   $231.60  
  Purchase #7 $129.80   11.508%   $144.7374   $144.74   $144.75   $144.70  
  7 purchase totals = $1,314.76       $1,434.3660   $1,434.37   $1,434.35   $1,434.20