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	$106.80	4.496%	$111.6017	$111.60	$111.60	$111.60
Purchase #2	$57.51	12.667%	$64.7948	$64.79	$64.80	$64.80
Purchase #3	$26.73	13.189%	$30.2554	$30.26	$30.25	$30.30
Purchase #4	$61.95	4.347%	$64.643	$64.64	$64.65	$64.60
Purchase #5	$152.52	10.194%	$168.0679	$168.07	$168.05	$168.10
Purchase #6	$64.82	13.782%	$73.7535	$73.75	$73.75	$73.80
Purchase #7	$200.83	4.402%	$209.6705	$209.67	$209.65	$209.70
7 purchase totals =	$671.16		$722.7868	$722.78	$722.75	$722.90