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	$133.40	4.644%	$139.5951	$139.60	$139.60	$139.60
Purchase #2	$35.65	13.191%	$40.3526	$40.35	$40.35	$40.40
Purchase #3	$194.78	7.156%	$208.7185	$208.72	$208.70	$208.70
Purchase #4	$249.98	9.181%	$272.9307	$272.93	$272.95	$272.90
Purchase #5	$158.29	9.648%	$173.5618	$173.56	$173.55	$173.60
Purchase #6	$203.49	9.653%	$223.1329	$223.13	$223.15	$223.10
Purchase #7	$42.44	11.183%	$47.1861	$47.19	$47.20	$47.20
7 purchase totals =	$1,018.03		$1,105.4777	$1,105.48	$1,105.50	$1,105.50