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	$204.40	9.120%	$223.0413	$223.04	$223.05	$223.00
Purchase #2	$146.82	7.813%	$158.291	$158.29	$158.30	$158.30
Purchase #3	$35.95	11.437%	$40.0616	$40.06	$40.05	$40.10
Purchase #4	$82.75	7.669%	$89.0961	$89.10	$89.10	$89.10
Purchase #5	$83.31	8.694%	$90.553	$90.55	$90.55	$90.60
Purchase #6	$217.72	10.431%	$240.4304	$240.43	$240.45	$240.40
Purchase #7	$99.76	5.763%	$105.5092	$105.51	$105.50	$105.50
7 purchase totals =	$870.71		$946.9826	$946.98	$947.00	$947.00