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 $61.84   4.827%   $64.825   $64.83   $64.85   $64.80  
  Purchase #2 $124.78   12.205%   $140.0094   $140.01   $140.00   $140.00  
  Purchase #3 $128.86   10.314%   $142.1506   $142.15   $142.15   $142.20  
  Purchase #4 $236.91   12.793%   $267.2179   $267.22   $267.20   $267.20  
  Purchase #5 $32.86   4.408%   $34.3085   $34.31   $34.30   $34.30  
  Purchase #6 $9.98   10.341%   $11.012   $11.01   $11.00   $11.00  
  Purchase #7 $82.44   3.707%   $85.4961   $85.50   $85.50   $85.50  
  7 purchase totals = $677.67       $745.0195   $745.03   $745.00   $745.00