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 $69.35   6.743%   $74.0263   $74.03   $74.05   $74.00  
  Purchase #2 $156.58   6.625%   $166.9534   $166.95   $166.95   $167.00  
  Purchase #3 $160.43   9.804%   $176.1586   $176.16   $176.15   $176.20  
  Purchase #4 $192.31   3.618%   $199.2678   $199.27   $199.25   $199.30  
  Purchase #5 $240.66   4.669%   $251.8964   $251.90   $251.90   $251.90  
  Purchase #6 $164.25   11.700%   $183.4673   $183.47   $183.45   $183.50  
  Purchase #7 $110.33   12.175%   $123.7627   $123.76   $123.75   $123.80  
  7 purchase totals = $1,093.91       $1,175.5325   $1,175.54   $1,175.50   $1,175.70