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	$50.62	7.447%	$54.3897	$54.39	$54.40	$54.40
Purchase #2	$173.81	4.150%	$181.0231	$181.02	$181.00	$181.00
Purchase #3	$191.55	12.153%	$214.8291	$214.83	$214.85	$214.80
Purchase #4	$28.38	13.768%	$32.2874	$32.29	$32.30	$32.30
Purchase #5	$202.53	11.458%	$225.7359	$225.74	$225.75	$225.70
Purchase #6	$140.85	12.488%	$158.4393	$158.44	$158.45	$158.40
Purchase #7	$24.95	11.783%	$27.8899	$27.89	$27.90	$27.90
7 purchase totals =	$812.69		$894.5944	$894.60	$894.65	$894.50