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	$97.53	6.532%	$103.9007	$103.90	$103.90	$103.90
Purchase #2	$173.80	6.654%	$185.3647	$185.36	$185.35	$185.40
Purchase #3	$58.56	5.187%	$61.5975	$61.60	$61.60	$61.60
Purchase #4	$9.44	7.592%	$10.1567	$10.16	$10.15	$10.20
Purchase #5	$122.80	4.155%	$127.9023	$127.90	$127.90	$127.90
Purchase #6	$85.37	3.665%	$88.4988	$88.50	$88.50	$88.50
Purchase #7	$179.68	8.560%	$195.0606	$195.06	$195.05	$195.10
7 purchase totals =	$727.18		$772.4813	$772.48	$772.45	$772.60