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	$162.76	10.130%	$179.2476	$179.25	$179.25	$179.20
Purchase #2	$244.29	3.694%	$253.3141	$253.31	$253.30	$253.30
Purchase #3	$64.46	12.118%	$72.2713	$72.27	$72.25	$72.30
Purchase #4	$123.46	11.862%	$138.1048	$138.10	$138.10	$138.10
Purchase #5	$177.45	9.560%	$194.4142	$194.41	$194.40	$194.40
Purchase #6	$120.37	6.400%	$128.0737	$128.07	$128.05	$128.10
Purchase #7	$92.58	8.194%	$100.166	$100.17	$100.15	$100.20
7 purchase totals =	$985.37		$1,065.5917	$1,065.58	$1,065.50	$1,065.60