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	$176.51	8.367%	$191.2786	$191.28	$191.30	$191.30
Purchase #2	$33.55	4.670%	$35.1168	$35.12	$35.10	$35.10
Purchase #3	$238.67	6.249%	$253.5845	$253.58	$253.60	$253.60
Purchase #4	$67.55	7.422%	$72.5636	$72.56	$72.55	$72.60
Purchase #5	$146.83	3.831%	$152.4551	$152.46	$152.45	$152.50
Purchase #6	$131.31	5.826%	$138.9601	$138.96	$138.95	$139.00
Purchase #7	$173.49	8.714%	$188.6079	$188.61	$188.60	$188.60
7 purchase totals =	$967.91		$1,032.5666	$1,032.57	$1,032.55	$1,032.70