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	$188.68	4.198%	$196.6008	$196.60	$196.60	$196.60
Purchase #2	$9.49	5.122%	$9.9761	$9.98	$10.00	$10.00
Purchase #3	$211.83	5.244%	$222.9384	$222.94	$222.95	$222.90
Purchase #4	$12.34	5.326%	$12.9972	$13.00	$13.00	$13.00
Purchase #5	$232.82	4.164%	$242.5146	$242.51	$242.50	$242.50
Purchase #6	$52.90	11.338%	$58.8978	$58.90	$58.90	$58.90
Purchase #7	$155.71	10.790%	$172.5111	$172.51	$172.50	$172.50
7 purchase totals =	$863.77		$916.4360	$916.44	$916.45	$916.40