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	$167.78	10.808%	$185.9137	$185.91	$185.90	$185.90
Purchase #2	$54.71	10.697%	$60.5623	$60.56	$60.55	$60.60
Purchase #3	$65.60	4.711%	$68.6904	$68.69	$68.70	$68.70
Purchase #4	$184.82	6.537%	$196.9017	$196.90	$196.90	$196.90
Purchase #5	$175.46	13.573%	$199.2752	$199.28	$199.30	$199.30
Purchase #6	$69.54	13.844%	$79.1671	$79.17	$79.15	$79.20
Purchase #7	$143.87	4.294%	$150.0478	$150.05	$150.05	$150.00
7 purchase totals =	$861.78		$940.5582	$940.56	$940.55	$940.60