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	$200.38	3.107%	$206.6058	$206.61	$206.60	$206.60
Purchase #2	$189.50	7.274%	$203.2842	$203.28	$203.30	$203.30
Purchase #3	$195.86	8.518%	$212.5434	$212.54	$212.55	$212.50
Purchase #4	$95.52	5.683%	$100.9484	$100.95	$100.95	$100.90
Purchase #5	$13.94	5.143%	$14.6569	$14.66	$14.65	$14.70
Purchase #6	$226.64	13.152%	$256.4477	$256.45	$256.45	$256.40
Purchase #7	$26.55	6.320%	$28.228	$28.23	$28.25	$28.20
7 purchase totals =	$948.39		$1,022.7144	$1,022.72	$1,022.75	$1,022.60