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	$18.40	5.503%	$19.4126	$19.41	$19.40	$19.40
Purchase #2	$200.43	11.641%	$223.7621	$223.76	$223.75	$223.80
Purchase #3	$122.57	3.495%	$126.8538	$126.85	$126.85	$126.90
Purchase #4	$11.73	3.343%	$12.1221	$12.12	$12.10	$12.10
Purchase #5	$41.95	6.104%	$44.5106	$44.51	$44.50	$44.50
Purchase #6	$171.40	11.369%	$190.8865	$190.89	$190.90	$190.90
Purchase #7	$114.41	8.104%	$123.6818	$123.68	$123.70	$123.70
7 purchase totals =	$680.89		$741.2295	$741.22	$741.20	$741.30