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 $53.39   7.749%   $57.5272   $57.53   $57.55   $57.50  
  Purchase #2 $115.41   7.380%   $123.9273   $123.93   $123.95   $123.90  
  Purchase #3 $220.81   6.722%   $235.6528   $235.65   $235.65   $235.70  
  Purchase #4 $35.98   9.677%   $39.4618   $39.46   $39.45   $39.50  
  Purchase #5 $209.69   11.166%   $233.104   $233.10   $233.10   $233.10  
  Purchase #6 $133.26   6.125%   $141.4222   $141.42   $141.40   $141.40  
  Purchase #7 $180.85   7.742%   $194.8514   $194.85   $194.85   $194.90  
  7 purchase totals = $949.39       $1,025.9467   $1,025.94   $1,025.95   $1,026.00