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	$178.26	12.222%	$200.0469	$200.05	$200.05	$200.00
Purchase #2	$22.51	4.438%	$23.509	$23.51	$23.50	$23.50
Purchase #3	$196.45	13.590%	$223.1476	$223.15	$223.15	$223.10
Purchase #4	$152.33	11.490%	$169.8327	$169.83	$169.85	$169.80
Purchase #5	$162.68	10.204%	$179.2799	$179.28	$179.30	$179.30
Purchase #6	$117.55	8.654%	$127.7228	$127.72	$127.70	$127.70
Purchase #7	$172.46	13.130%	$195.104	$195.10	$195.10	$195.10
7 purchase totals =	$1,002.24		$1,118.6429	$1,118.64	$1,118.65	$1,118.50