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	$12.85	10.370%	$14.1825	$14.18	$14.20	$14.20
Purchase #2	$89.38	11.338%	$99.5139	$99.51	$99.50	$99.50
Purchase #3	$178.85	6.629%	$190.706	$190.71	$190.70	$190.70
Purchase #4	$240.36	13.760%	$273.4335	$273.43	$273.45	$273.40
Purchase #5	$238.61	10.700%	$264.1413	$264.14	$264.15	$264.10
Purchase #6	$190.63	11.142%	$211.87	$211.87	$211.85	$211.90
Purchase #7	$14.97	7.234%	$16.0529	$16.05	$16.05	$16.10
7 purchase totals =	$965.65		$1,069.9001	$1,069.89	$1,069.90	$1,069.90