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	$157.83	9.170%	$172.303	$172.30	$172.30	$172.30
Purchase #2	$91.42	9.667%	$100.2576	$100.26	$100.25	$100.30
Purchase #3	$193.33	5.845%	$204.6301	$204.63	$204.65	$204.60
Purchase #4	$154.40	6.323%	$164.1627	$164.16	$164.15	$164.20
Purchase #5	$7.40	8.205%	$8.0072	$8.01	$8.00	$8.00
Purchase #6	$145.48	10.244%	$160.383	$160.38	$160.40	$160.40
Purchase #7	$182.63	5.414%	$192.5176	$192.52	$192.50	$192.50
7 purchase totals =	$932.49		$1,002.2612	$1,002.26	$1,002.25	$1,002.30