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	$147.67	13.186%	$167.1418	$167.14	$167.15	$167.10
Purchase #2	$151.61	4.649%	$158.6583	$158.66	$158.65	$158.70
Purchase #3	$217.48	7.444%	$233.6692	$233.67	$233.65	$233.70
Purchase #4	$221.26	9.588%	$242.4744	$242.47	$242.45	$242.50
Purchase #5	$16.69	12.548%	$18.7843	$18.78	$18.80	$18.80
Purchase #6	$128.48	12.784%	$144.9049	$144.90	$144.90	$144.90
Purchase #7	$83.27	5.411%	$87.7757	$87.78	$87.80	$87.80
7 purchase totals =	$966.46		$1,053.4086	$1,053.40	$1,053.40	$1,053.50