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 $213.74   10.437%   $236.048   $236.05   $236.05   $236.00  
  Purchase #2 $49.78   9.434%   $54.4762   $54.48   $54.50   $54.50  
  Purchase #3 $34.69   11.738%   $38.7619   $38.76   $38.75   $38.80  
  Purchase #4 $54.85   10.783%   $60.7645   $60.76   $60.75   $60.80  
  Purchase #5 $9.48   12.120%   $10.629   $10.63   $10.65   $10.60  
  Purchase #6 $232.39   3.828%   $241.2859   $241.29   $241.30   $241.30  
  Purchase #7 $109.43   3.251%   $112.9876   $112.99   $113.00   $113.00  
  7 purchase totals = $704.36       $754.9531   $754.96   $755.00   $755.00