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	$55.58	11.290%	$61.855	$61.86	$61.85	$61.90
Purchase #2	$89.58	12.256%	$100.5589	$100.56	$100.55	$100.60
Purchase #3	$37.66	12.649%	$42.4236	$42.42	$42.40	$42.40
Purchase #4	$200.65	11.795%	$224.3167	$224.32	$224.30	$224.30
Purchase #5	$53.77	6.466%	$57.2468	$57.25	$57.25	$57.20
Purchase #6	$14.39	8.635%	$15.6326	$15.63	$15.65	$15.60
Purchase #7	$11.54	7.457%	$12.4005	$12.40	$12.40	$12.40
7 purchase totals =	$463.17		$514.4341	$514.44	$514.40	$514.40