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 $62.43   4.184%   $65.0421   $65.04   $65.05   $65.00  
  Purchase #2 $86.34   11.734%   $96.4711   $96.47   $96.45   $96.50  
  Purchase #3 $140.94   6.513%   $150.1194   $150.12   $150.10   $150.10  
  Purchase #4 $234.41   11.177%   $260.61   $260.61   $260.60   $260.60  
  Purchase #5 $130.33   9.515%   $142.7309   $142.73   $142.75   $142.70  
  Purchase #6 $149.39   13.795%   $169.9984   $170.00   $170.00   $170.00  
  Purchase #7 $167.80   4.595%   $175.5104   $175.51   $175.50   $175.50  
  7 purchase totals = $971.64       $1,060.4823   $1,060.48   $1,060.45   $1,060.40