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	$136.71	6.734%	$145.9161	$145.92	$145.90	$145.90
Purchase #2	$196.52	7.690%	$211.6324	$211.63	$211.65	$211.60
Purchase #3	$130.74	11.426%	$145.6784	$145.68	$145.70	$145.70
Purchase #4	$161.76	6.641%	$172.5025	$172.50	$172.50	$172.50
Purchase #5	$118.40	7.385%	$127.1438	$127.14	$127.15	$127.10
Purchase #6	$183.47	9.121%	$200.2043	$200.20	$200.20	$200.20
Purchase #7	$12.64	12.546%	$14.2258	$14.23	$14.25	$14.20
7 purchase totals =	$940.24		$1,017.3033	$1,017.30	$1,017.35	$1,017.20