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	$89.72	10.401%	$99.0518	$99.05	$99.05	$99.10
Purchase #2	$93.81	7.325%	$100.6816	$100.68	$100.70	$100.70
Purchase #3	$28.29	13.770%	$32.1855	$32.19	$32.20	$32.20
Purchase #4	$23.57	5.834%	$24.9451	$24.95	$24.95	$24.90
Purchase #5	$182.72	13.128%	$206.7075	$206.71	$206.70	$206.70
Purchase #6	$28.43	13.714%	$32.3289	$32.33	$32.35	$32.30
Purchase #7	$213.45	9.426%	$233.5698	$233.57	$233.55	$233.60
7 purchase totals =	$659.99		$729.4702	$729.48	$729.50	$729.50