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 $67.87   8.535%   $73.6627   $73.66   $73.65   $73.70  
  Purchase #2 $201.98   5.626%   $213.3434   $213.34   $213.35   $213.30  
  Purchase #3 $169.37   12.385%   $190.3465   $190.35   $190.35   $190.30  
  Purchase #4 $147.56   13.727%   $167.8156   $167.82   $167.80   $167.80  
  Purchase #5 $158.64   10.543%   $175.3654   $175.37   $175.35   $175.40  
  Purchase #6 $187.49   7.663%   $201.8574   $201.86   $201.85   $201.90  
  Purchase #7 $189.92   5.717%   $200.7777   $200.78   $200.80   $200.80  
  7 purchase totals = $1,122.83       $1,223.1687   $1,223.18   $1,223.15   $1,223.20