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	$202.32	8.316%	$219.1449	$219.14	$219.15	$219.10
Purchase #2	$93.61	7.207%	$100.3565	$100.36	$100.35	$100.40
Purchase #3	$33.25	3.497%	$34.4128	$34.41	$34.40	$34.40
Purchase #4	$68.99	4.617%	$72.1753	$72.18	$72.20	$72.20
Purchase #5	$100.60	10.659%	$111.323	$111.32	$111.30	$111.30
Purchase #6	$67.35	6.465%	$71.7042	$71.70	$71.70	$71.70
Purchase #7	$105.92	13.582%	$120.3061	$120.31	$120.30	$120.30
7 purchase totals =	$672.04		$729.4228	$729.42	$729.40	$729.40