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	$53.70	7.132%	$57.5299	$57.53	$57.55	$57.50
Purchase #2	$204.45	8.301%	$221.4214	$221.42	$221.40	$221.40
Purchase #3	$90.33	10.453%	$99.7722	$99.77	$99.75	$99.80
Purchase #4	$227.90	7.166%	$244.2313	$244.23	$244.25	$244.20
Purchase #5	$50.35	4.433%	$52.582	$52.58	$52.60	$52.60
Purchase #6	$220.64	13.860%	$251.2207	$251.22	$251.20	$251.20
Purchase #7	$89.37	12.650%	$100.6753	$100.68	$100.70	$100.70
7 purchase totals =	$936.74		$1,027.4328	$1,027.43	$1,027.45	$1,027.40