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	$228.69	5.520%	$241.3137	$241.31	$241.30	$241.30
Purchase #2	$31.87	12.472%	$35.8448	$35.84	$35.85	$35.80
Purchase #3	$137.89	5.364%	$145.2864	$145.29	$145.30	$145.30
Purchase #4	$211.44	10.401%	$233.4319	$233.43	$233.45	$233.40
Purchase #5	$167.51	6.726%	$178.7767	$178.78	$178.80	$178.80
Purchase #6	$94.51	5.800%	$99.9916	$99.99	$100.00	$100.00
Purchase #7	$219.26	5.259%	$230.7909	$230.79	$230.80	$230.80
7 purchase totals =	$1,091.17		$1,165.4360	$1,165.43	$1,165.50	$1,165.40