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	$76.42	8.483%	$82.9027	$82.90	$82.90	$82.90
Purchase #2	$120.26	5.728%	$127.1485	$127.15	$127.15	$127.10
Purchase #3	$15.60	4.634%	$16.3229	$16.32	$16.30	$16.30
Purchase #4	$17.29	8.628%	$18.7818	$18.78	$18.80	$18.80
Purchase #5	$227.74	12.804%	$256.8998	$256.90	$256.90	$256.90
Purchase #6	$6.58	6.749%	$7.0241	$7.02	$7.00	$7.00
Purchase #7	$64.28	5.827%	$68.0256	$68.03	$68.05	$68.00
7 purchase totals =	$528.17		$577.1054	$577.10	$577.10	$577.00