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	$119.72	6.570%	$127.5856	$127.59	$127.60	$127.60
Purchase #2	$118.77	6.307%	$126.2608	$126.26	$126.25	$126.30
Purchase #3	$184.66	6.865%	$197.3369	$197.34	$197.35	$197.30
Purchase #4	$80.67	11.793%	$90.1834	$90.18	$90.20	$90.20
Purchase #5	$225.31	3.204%	$232.5289	$232.53	$232.55	$232.50
Purchase #6	$60.66	11.644%	$67.7233	$67.72	$67.70	$67.70
Purchase #7	$108.30	4.252%	$112.9049	$112.90	$112.90	$112.90
7 purchase totals =	$898.09		$954.5238	$954.52	$954.55	$954.50