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 $176.82   9.497%   $193.6126   $193.61   $193.60   $193.60  
  Purchase #2 $41.54   13.415%   $47.1126   $47.11   $47.10   $47.10  
  Purchase #3 $86.73   11.202%   $96.4455   $96.45   $96.45   $96.40  
  Purchase #4 $170.51   8.614%   $185.1977   $185.20   $185.20   $185.20  
  Purchase #5 $165.28   7.652%   $177.9272   $177.93   $177.95   $177.90  
  Purchase #6 $232.30   11.547%   $259.1237   $259.12   $259.10   $259.10  
  Purchase #7 $211.67   4.325%   $220.8247   $220.82   $220.80   $220.80  
  7 purchase totals = $1,084.85       $1,180.2440   $1,180.24   $1,180.20   $1,180.10