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	$145.71	7.343%	$156.4095	$156.41	$156.40	$156.40
Purchase #2	$130.63	10.568%	$144.435	$144.44	$144.45	$144.40
Purchase #3	$184.43	3.707%	$191.2668	$191.27	$191.25	$191.30
Purchase #4	$151.55	5.209%	$159.4442	$159.44	$159.45	$159.40
Purchase #5	$91.50	8.829%	$99.5785	$99.58	$99.60	$99.60
Purchase #6	$90.47	13.723%	$102.8852	$102.89	$102.90	$102.90
Purchase #7	$121.71	7.757%	$131.151	$131.15	$131.15	$131.20
7 purchase totals =	$916.00		$985.1702	$985.18	$985.20	$985.20