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 $117.82   7.415%   $126.5564   $126.56   $126.55   $126.60  
  Purchase #2 $58.39   7.370%   $62.6933   $62.69   $62.70   $62.70  
  Purchase #3 $8.84   9.862%   $9.7118   $9.71   $9.70   $9.70  
  Purchase #4 $157.30   3.486%   $162.7835   $162.78   $162.80   $162.80  
  Purchase #5 $107.36   9.514%   $117.5742   $117.57   $117.55   $117.60  
  Purchase #6 $239.78   8.186%   $259.4084   $259.41   $259.40   $259.40  
  Purchase #7 $156.41   8.173%   $169.1934   $169.19   $169.20   $169.20  
  7 purchase totals = $845.90       $907.9210   $907.91   $907.90   $908.00