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	$226.43	9.247%	$247.368	$247.37	$247.35	$247.40
Purchase #2	$51.27	7.449%	$55.0891	$55.09	$55.10	$55.10
Purchase #3	$216.46	13.375%	$245.4115	$245.41	$245.40	$245.40
Purchase #4	$230.67	4.567%	$241.2047	$241.20	$241.20	$241.20
Purchase #5	$55.89	5.735%	$59.0953	$59.10	$59.10	$59.10
Purchase #6	$113.54	11.858%	$127.0036	$127.00	$127.00	$127.00
Purchase #7	$49.64	3.713%	$51.4831	$51.48	$51.50	$51.50
7 purchase totals =	$943.90		$1,026.6553	$1,026.65	$1,026.65	$1,026.70