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 $174.67   11.175%   $194.1894   $194.19   $194.20   $194.20  
  Purchase #2 $116.46   5.469%   $122.8292   $122.83   $122.85   $122.80  
  Purchase #3 $159.63   7.763%   $172.0221   $172.02   $172.00   $172.00  
  Purchase #4 $75.54   7.623%   $81.2984   $81.30   $81.30   $81.30  
  Purchase #5 $204.69   13.554%   $232.4337   $232.43   $232.45   $232.40  
  Purchase #6 $104.63   10.175%   $115.2761   $115.28   $115.30   $115.30  
  Purchase #7 $242.99   8.354%   $263.2894   $263.29   $263.30   $263.30  
  7 purchase totals = $1,078.61       $1,181.3383   $1,181.34   $1,181.40   $1,181.30