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 $182.59   13.507%   $207.2524   $207.25   $207.25   $207.30  
  Purchase #2 $56.74   9.627%   $62.2024   $62.20   $62.20   $62.20  
  Purchase #3 $205.98   9.111%   $224.7468   $224.75   $224.75   $224.70  
  Purchase #4 $180.90   10.164%   $199.2867   $199.29   $199.30   $199.30  
  Purchase #5 $172.92   4.632%   $180.9297   $180.93   $180.95   $180.90  
  Purchase #6 $68.36   9.202%   $74.6505   $74.65   $74.65   $74.70  
  Purchase #7 $194.97   3.465%   $201.7257   $201.73   $201.75   $201.70  
  7 purchase totals = $1,062.46       $1,150.7942   $1,150.80   $1,150.85   $1,150.80