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	$57.56	10.188%	$63.4242	$63.42	$63.40	$63.40
Purchase #2	$235.41	13.449%	$267.0703	$267.07	$267.05	$267.10
Purchase #3	$92.30	12.181%	$103.5431	$103.54	$103.55	$103.50
Purchase #4	$111.86	4.772%	$117.198	$117.20	$117.20	$117.20
Purchase #5	$135.33	12.674%	$152.4817	$152.48	$152.50	$152.50
Purchase #6	$165.76	4.215%	$172.7468	$172.75	$172.75	$172.70
Purchase #7	$212.78	4.861%	$223.1232	$223.12	$223.10	$223.10
7 purchase totals =	$1,011.00		$1,099.5873	$1,099.58	$1,099.55	$1,099.50