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	$123.63	3.429%	$127.8693	$127.87	$127.85	$127.90
Purchase #2	$172.46	8.377%	$186.907	$186.91	$186.90	$186.90
Purchase #3	$23.89	8.759%	$25.9825	$25.98	$26.00	$26.00
Purchase #4	$80.40	6.609%	$85.7136	$85.71	$85.70	$85.70
Purchase #5	$33.94	11.649%	$37.8937	$37.89	$37.90	$37.90
Purchase #6	$232.83	9.385%	$254.6811	$254.68	$254.70	$254.70
Purchase #7	$58.70	6.285%	$62.3893	$62.39	$62.40	$62.40
7 purchase totals =	$725.85		$781.4365	$781.43	$781.45	$781.50