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	$114.29	13.120%	$129.2848	$129.28	$129.30	$129.30
Purchase #2	$87.95	4.353%	$91.7785	$91.78	$91.80	$91.80
Purchase #3	$201.89	5.286%	$212.5619	$212.56	$212.55	$212.60
Purchase #4	$144.64	9.340%	$158.1494	$158.15	$158.15	$158.10
Purchase #5	$110.33	11.770%	$123.3158	$123.32	$123.30	$123.30
Purchase #6	$185.52	7.805%	$199.9998	$200.00	$200.00	$200.00
Purchase #7	$172.65	13.233%	$195.4968	$195.50	$195.50	$195.50
7 purchase totals =	$1,017.27		$1,110.5870	$1,110.59	$1,110.60	$1,110.60