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	$247.98	3.466%	$256.575	$256.58	$256.60	$256.60
Purchase #2	$28.37	4.659%	$29.6918	$29.69	$29.70	$29.70
Purchase #3	$158.67	12.392%	$178.3324	$178.33	$178.35	$178.30
Purchase #4	$52.33	13.463%	$59.3752	$59.38	$59.40	$59.40
Purchase #5	$145.79	3.815%	$151.3519	$151.35	$151.35	$151.40
Purchase #6	$96.53	4.345%	$100.7242	$100.72	$100.70	$100.70
Purchase #7	$10.94	13.645%	$12.4328	$12.43	$12.45	$12.40
7 purchase totals =	$740.61		$788.4833	$788.48	$788.55	$788.50