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	$92.75	13.710%	$105.466	$105.47	$105.45	$105.50
Purchase #2	$85.38	10.746%	$94.5549	$94.55	$94.55	$94.60
Purchase #3	$58.32	13.405%	$66.1378	$66.14	$66.15	$66.10
Purchase #4	$134.41	5.227%	$141.4356	$141.44	$141.45	$141.40
Purchase #5	$102.81	3.227%	$106.1277	$106.13	$106.15	$106.10
Purchase #6	$18.38	9.459%	$20.1186	$20.12	$20.10	$20.10
Purchase #7	$138.38	9.418%	$151.4126	$151.41	$151.40	$151.40
7 purchase totals =	$630.43		$685.2532	$685.26	$685.25	$685.20