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	$59.81	8.217%	$64.7246	$64.72	$64.70	$64.70
Purchase #2	$164.44	10.568%	$181.818	$181.82	$181.80	$181.80
Purchase #3	$11.52	10.698%	$12.7524	$12.75	$12.75	$12.80
Purchase #4	$212.85	9.735%	$233.5709	$233.57	$233.55	$233.60
Purchase #5	$82.28	4.360%	$85.8674	$85.87	$85.85	$85.90
Purchase #6	$46.26	4.647%	$48.4097	$48.41	$48.40	$48.40
Purchase #7	$53.26	7.814%	$57.4217	$57.42	$57.40	$57.40
7 purchase totals =	$630.42		$684.5647	$684.56	$684.45	$684.60