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	$205.76	8.821%	$223.9101	$223.91	$223.90	$223.90
Purchase #2	$193.57	12.842%	$218.4283	$218.43	$218.45	$218.40
Purchase #3	$150.97	8.733%	$164.1542	$164.15	$164.15	$164.20
Purchase #4	$124.78	7.583%	$134.2421	$134.24	$134.25	$134.20
Purchase #5	$114.35	11.693%	$127.7209	$127.72	$127.70	$127.70
Purchase #6	$28.44	10.411%	$31.4009	$31.40	$31.40	$31.40
Purchase #7	$237.75	12.582%	$267.6637	$267.66	$267.65	$267.70
7 purchase totals =	$1,055.62		$1,167.5202	$1,167.51	$1,167.50	$1,167.50