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	$132.33	3.140%	$136.4852	$136.49	$136.50	$136.50
Purchase #2	$174.61	11.651%	$194.9538	$194.95	$194.95	$195.00
Purchase #3	$228.60	11.142%	$254.0706	$254.07	$254.05	$254.10
Purchase #4	$144.40	4.649%	$151.1132	$151.11	$151.10	$151.10
Purchase #5	$175.43	7.427%	$188.4592	$188.46	$188.45	$188.50
Purchase #6	$99.95	11.844%	$111.7881	$111.79	$111.80	$111.80
Purchase #7	$242.58	12.473%	$272.837	$272.84	$272.85	$272.80
7 purchase totals =	$1,197.90		$1,309.7071	$1,309.71	$1,309.70	$1,309.80