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	$138.29	9.427%	$151.3266	$151.33	$151.35	$151.30
Purchase #2	$32.67	4.143%	$34.0235	$34.02	$34.00	$34.00
Purchase #3	$18.66	10.603%	$20.6385	$20.64	$20.65	$20.60
Purchase #4	$82.59	9.128%	$90.1288	$90.13	$90.15	$90.10
Purchase #5	$112.55	13.836%	$128.1224	$128.12	$128.10	$128.10
Purchase #6	$21.88	5.268%	$23.0326	$23.03	$23.05	$23.00
Purchase #7	$61.79	5.758%	$65.3479	$65.35	$65.35	$65.30
7 purchase totals =	$468.43		$512.6203	$512.62	$512.65	$512.40