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	$86.76	6.697%	$92.5703	$92.57	$92.55	$92.60
Purchase #2	$75.70	3.644%	$78.4585	$78.46	$78.45	$78.50
Purchase #3	$77.87	6.584%	$82.997	$83.00	$83.00	$83.00
Purchase #4	$106.91	3.145%	$110.2723	$110.27	$110.25	$110.30
Purchase #5	$195.94	9.422%	$214.4015	$214.40	$214.40	$214.40
Purchase #6	$164.74	11.387%	$183.4989	$183.50	$183.50	$183.50
Purchase #7	$33.89	9.404%	$37.077	$37.08	$37.10	$37.10
7 purchase totals =	$741.81		$799.2755	$799.28	$799.25	$799.40