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 $187.29   8.238%   $202.719   $202.72   $202.70   $202.70  
  Purchase #2 $70.90   7.457%   $76.187   $76.19   $76.20   $76.20  
  Purchase #3 $11.73   7.310%   $12.5875   $12.59   $12.60   $12.60  
  Purchase #4 $108.53   5.192%   $114.1649   $114.16   $114.15   $114.20  
  Purchase #5 $156.88   6.873%   $167.6624   $167.66   $167.65   $167.70  
  Purchase #6 $154.25   6.660%   $164.5231   $164.52   $164.50   $164.50  
  Purchase #7 $186.68   4.445%   $194.9779   $194.98   $195.00   $195.00  
  7 purchase totals = $876.26       $932.8218   $932.82   $932.80   $932.90