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	$90.53	10.688%	$100.2058	$100.21	$100.20	$100.20
Purchase #2	$209.93	4.690%	$219.7757	$219.78	$219.80	$219.80
Purchase #3	$10.51	4.243%	$10.9559	$10.96	$10.95	$11.00
Purchase #4	$99.65	6.690%	$106.3166	$106.32	$106.30	$106.30
Purchase #5	$18.92	11.868%	$21.1654	$21.17	$21.15	$21.20
Purchase #6	$71.43	11.237%	$79.4566	$79.46	$79.45	$79.50
Purchase #7	$198.78	10.493%	$219.638	$219.64	$219.65	$219.60
7 purchase totals =	$699.75		$757.5140	$757.54	$757.50	$757.60