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	$179.85	5.873%	$190.4126	$190.41	$190.40	$190.40
Purchase #2	$146.88	3.466%	$151.9709	$151.97	$151.95	$152.00
Purchase #3	$230.74	11.166%	$256.5044	$256.50	$256.50	$256.50
Purchase #4	$131.37	10.840%	$145.6105	$145.61	$145.60	$145.60
Purchase #5	$132.94	3.460%	$137.5397	$137.54	$137.55	$137.50
Purchase #6	$212.33	10.786%	$235.2319	$235.23	$235.25	$235.20
Purchase #7	$224.61	11.752%	$251.0062	$251.01	$251.00	$251.00
7 purchase totals =	$1,258.72		$1,368.2762	$1,368.27	$1,368.25	$1,368.20