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	$103.36	12.396%	$116.1725	$116.17	$116.15	$116.20
Purchase #2	$143.53	3.836%	$149.0358	$149.04	$149.05	$149.00
Purchase #3	$132.52	11.177%	$147.3318	$147.33	$147.35	$147.30
Purchase #4	$229.56	9.482%	$251.3269	$251.33	$251.35	$251.30
Purchase #5	$120.61	5.525%	$127.2737	$127.27	$127.25	$127.30
Purchase #6	$103.96	7.656%	$111.9192	$111.92	$111.90	$111.90
Purchase #7	$198.83	12.511%	$223.7056	$223.71	$223.70	$223.70
7 purchase totals =	$1,032.37		$1,126.7655	$1,126.77	$1,126.75	$1,126.70