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	$214.36	3.519%	$221.9033	$221.90	$221.90	$221.90
Purchase #2	$23.75	11.509%	$26.4834	$26.48	$26.50	$26.50
Purchase #3	$9.76	6.198%	$10.3649	$10.36	$10.35	$10.40
Purchase #4	$99.52	6.163%	$105.6534	$105.65	$105.65	$105.70
Purchase #5	$74.45	11.518%	$83.0252	$83.03	$83.05	$83.00
Purchase #6	$36.86	13.695%	$41.908	$41.91	$41.90	$41.90
Purchase #7	$181.61	8.150%	$196.4112	$196.41	$196.40	$196.40
7 purchase totals =	$640.31		$685.7494	$685.74	$685.75	$685.80