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	$100.29	4.713%	$105.0167	$105.02	$105.00	$105.00
Purchase #2	$170.29	5.527%	$179.7019	$179.70	$179.70	$179.70
Purchase #3	$20.51	13.541%	$23.2873	$23.29	$23.30	$23.30
Purchase #4	$212.67	5.572%	$224.52	$224.52	$224.50	$224.50
Purchase #5	$140.82	7.421%	$151.2703	$151.27	$151.25	$151.30
Purchase #6	$44.43	13.797%	$50.56	$50.56	$50.55	$50.60
Purchase #7	$142.77	12.107%	$160.0552	$160.06	$160.05	$160.10
7 purchase totals =	$831.78		$894.4114	$894.42	$894.35	$894.50