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 $247.94   5.645%   $261.9362   $261.94   $261.95   $261.90  
  Purchase #2 $44.29   6.854%   $47.3256   $47.33   $47.35   $47.30  
  Purchase #3 $49.88   4.326%   $52.0378   $52.04   $52.05   $52.00  
  Purchase #4 $194.51   9.470%   $212.9301   $212.93   $212.95   $212.90  
  Purchase #5 $154.27   9.530%   $168.9719   $168.97   $168.95   $169.00  
  Purchase #6 $122.77   7.854%   $132.4124   $132.41   $132.40   $132.40  
  Purchase #7 $144.25   11.198%   $160.4031   $160.40   $160.40   $160.40  
  7 purchase totals = $957.91       $1,036.0171   $1,036.02   $1,036.05   $1,035.90