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	$126.34	3.244%	$130.4385	$130.44	$130.45	$130.40
Purchase #2	$163.64	10.540%	$180.8877	$180.89	$180.90	$180.90
Purchase #3	$198.55	11.538%	$221.4587	$221.46	$221.45	$221.50
Purchase #4	$180.72	8.195%	$195.53	$195.53	$195.55	$195.50
Purchase #5	$172.82	10.194%	$190.4373	$190.44	$190.45	$190.40
Purchase #6	$111.68	13.814%	$127.1075	$127.11	$127.10	$127.10
Purchase #7	$154.62	13.297%	$175.1798	$175.18	$175.20	$175.20
7 purchase totals =	$1,108.37		$1,221.0395	$1,221.05	$1,221.10	$1,221.00