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	$110.56	4.353%	$115.3727	$115.37	$115.35	$115.40
Purchase #2	$37.98	11.251%	$42.2531	$42.25	$42.25	$42.30
Purchase #3	$233.75	7.514%	$251.314	$251.31	$251.30	$251.30
Purchase #4	$174.94	9.605%	$191.743	$191.74	$191.75	$191.70
Purchase #5	$142.81	11.274%	$158.9104	$158.91	$158.90	$158.90
Purchase #6	$159.42	4.514%	$166.6162	$166.62	$166.60	$166.60
Purchase #7	$113.25	5.336%	$119.293	$119.29	$119.30	$119.30
7 purchase totals =	$972.71		$1,045.5024	$1,045.49	$1,045.45	$1,045.50