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 $68.69   7.679%   $73.9647   $73.96   $73.95   $74.00  
  Purchase #2 $174.70   11.479%   $194.7538   $194.75   $194.75   $194.80  
  Purchase #3 $199.37   10.191%   $219.6878   $219.69   $219.70   $219.70  
  Purchase #4 $136.53   13.269%   $154.6462   $154.65   $154.65   $154.60  
  Purchase #5 $164.78   12.594%   $185.5324   $185.53   $185.55   $185.50  
  Purchase #6 $99.31   8.515%   $107.7662   $107.77   $107.75   $107.80  
  Purchase #7 $109.25   3.208%   $112.7547   $112.75   $112.75   $112.80  
  7 purchase totals = $952.63       $1,049.1058   $1,049.10   $1,049.10   $1,049.20