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	$243.38	4.589%	$254.5487	$254.55	$254.55	$254.50
Purchase #2	$201.54	11.663%	$225.0456	$225.05	$225.05	$225.00
Purchase #3	$10.90	6.346%	$11.5917	$11.59	$11.60	$11.60
Purchase #4	$202.52	9.805%	$222.3771	$222.38	$222.40	$222.40
Purchase #5	$227.57	5.503%	$240.0932	$240.09	$240.10	$240.10
Purchase #6	$20.56	10.845%	$22.7897	$22.79	$22.80	$22.80
Purchase #7	$85.82	7.316%	$92.0986	$92.10	$92.10	$92.10
7 purchase totals =	$992.29		$1,068.5446	$1,068.55	$1,068.60	$1,068.50