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	$202.39	5.106%	$212.724	$212.72	$212.70	$212.70
Purchase #2	$27.51	11.527%	$30.6811	$30.68	$30.70	$30.70
Purchase #3	$52.65	13.841%	$59.9373	$59.94	$59.95	$59.90
Purchase #4	$138.76	5.205%	$145.9825	$145.98	$146.00	$146.00
Purchase #5	$198.84	12.108%	$222.9155	$222.92	$222.90	$222.90
Purchase #6	$185.79	3.813%	$192.8742	$192.87	$192.85	$192.90
Purchase #7	$131.95	4.420%	$137.7822	$137.78	$137.80	$137.80
7 purchase totals =	$937.89		$1,002.8968	$1,002.89	$1,002.90	$1,002.90