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	$94.48	7.254%	$101.3336	$101.33	$101.35	$101.30
Purchase #2	$105.98	5.579%	$111.8926	$111.89	$111.90	$111.90
Purchase #3	$58.89	6.152%	$62.5129	$62.51	$62.50	$62.50
Purchase #4	$10.35	5.477%	$10.9169	$10.92	$10.90	$10.90
Purchase #5	$82.58	11.784%	$92.3112	$92.31	$92.30	$92.30
Purchase #6	$159.31	8.275%	$172.4929	$172.49	$172.50	$172.50
Purchase #7	$93.85	4.252%	$97.8405	$97.84	$97.85	$97.80
7 purchase totals =	$605.44		$649.3006	$649.29	$649.30	$649.20