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	$242.33	4.840%	$254.0588	$254.06	$254.05	$254.10
Purchase #2	$158.88	5.525%	$167.6581	$167.66	$167.65	$167.70
Purchase #3	$216.53	6.401%	$230.3901	$230.39	$230.40	$230.40
Purchase #4	$135.40	13.681%	$153.9241	$153.92	$153.90	$153.90
Purchase #5	$215.61	7.202%	$231.1382	$231.14	$231.15	$231.10
Purchase #6	$129.27	6.497%	$137.6687	$137.67	$137.65	$137.70
Purchase #7	$52.54	4.745%	$55.033	$55.03	$55.05	$55.00
7 purchase totals =	$1,150.56		$1,229.8710	$1,229.87	$1,229.85	$1,229.90