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 $71.36   7.531%   $76.7341   $76.73   $76.75   $76.70  
  Purchase #2 $219.82   9.372%   $240.4215   $240.42   $240.40   $240.40  
  Purchase #3 $169.75   8.552%   $184.267   $184.27   $184.25   $184.30  
  Purchase #4 $247.43   4.637%   $258.9033   $258.90   $258.90   $258.90  
  Purchase #5 $46.62   10.670%   $51.5944   $51.59   $51.60   $51.60  
  Purchase #6 $141.84   5.580%   $149.7547   $149.75   $149.75   $149.80  
  Purchase #7 $221.80   6.233%   $235.6248   $235.62   $235.60   $235.60  
  7 purchase totals = $1,118.62       $1,197.2998   $1,197.28   $1,197.25   $1,197.30