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	$67.66	6.559%	$72.0978	$72.10	$72.10	$72.10
Purchase #2	$226.52	8.109%	$244.8885	$244.89	$244.90	$244.90
Purchase #3	$235.85	6.599%	$251.4137	$251.41	$251.40	$251.40
Purchase #4	$80.92	12.613%	$91.1264	$91.13	$91.15	$91.10
Purchase #5	$190.63	3.486%	$197.2754	$197.28	$197.30	$197.30
Purchase #6	$90.92	5.860%	$96.2479	$96.25	$96.25	$96.20
Purchase #7	$100.77	12.657%	$113.5245	$113.52	$113.50	$113.50
7 purchase totals =	$993.27		$1,066.5742	$1,066.58	$1,066.60	$1,066.50