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	$176.75	4.227%	$184.2212	$184.22	$184.20	$184.20
Purchase #2	$17.25	6.566%	$18.3826	$18.38	$18.40	$18.40
Purchase #3	$13.28	10.109%	$14.6225	$14.62	$14.60	$14.60
Purchase #4	$81.38	9.775%	$89.3349	$89.33	$89.35	$89.30
Purchase #5	$45.52	11.214%	$50.6246	$50.62	$50.60	$50.60
Purchase #6	$81.95	12.845%	$92.4765	$92.48	$92.50	$92.50
Purchase #7	$167.64	12.428%	$188.4743	$188.47	$188.45	$188.50
7 purchase totals =	$583.77		$638.1366	$638.12	$638.10	$638.10