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	$226.74	11.663%	$253.1847	$253.18	$253.20	$253.20
Purchase #2	$78.62	13.777%	$89.4515	$89.45	$89.45	$89.50
Purchase #3	$100.95	4.246%	$105.2363	$105.24	$105.25	$105.20
Purchase #4	$208.96	4.190%	$217.7154	$217.72	$217.70	$217.70
Purchase #5	$129.37	8.619%	$140.5204	$140.52	$140.50	$140.50
Purchase #6	$50.48	10.751%	$55.9071	$55.91	$55.90	$55.90
Purchase #7	$178.60	6.416%	$190.059	$190.06	$190.05	$190.10
7 purchase totals =	$973.72		$1,052.0744	$1,052.08	$1,052.05	$1,052.10