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	$85.74	10.694%	$94.909	$94.91	$94.90	$94.90
Purchase #2	$131.30	12.830%	$148.1458	$148.15	$148.15	$148.10
Purchase #3	$11.70	7.530%	$12.581	$12.58	$12.60	$12.60
Purchase #4	$186.29	6.535%	$198.4641	$198.46	$198.45	$198.50
Purchase #5	$61.41	11.456%	$68.4451	$68.45	$68.45	$68.40
Purchase #6	$118.35	7.740%	$127.5103	$127.51	$127.50	$127.50
Purchase #7	$153.33	3.580%	$158.8192	$158.82	$158.80	$158.80
7 purchase totals =	$748.12		$808.8745	$808.88	$808.85	$808.80