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	$118.88	3.373%	$122.8898	$122.89	$122.90	$122.90
Purchase #2	$89.49	11.431%	$99.7196	$99.72	$99.70	$99.70
Purchase #3	$181.72	8.710%	$197.5478	$197.55	$197.55	$197.50
Purchase #4	$216.56	6.175%	$229.9326	$229.93	$229.95	$229.90
Purchase #5	$164.38	4.666%	$172.05	$172.05	$172.05	$172.10
Purchase #6	$228.87	9.844%	$251.4	$251.40	$251.40	$251.40
Purchase #7	$62.57	7.172%	$67.0575	$67.06	$67.05	$67.10
7 purchase totals =	$1,062.47		$1,140.5973	$1,140.60	$1,140.60	$1,140.60