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	$140.95	13.280%	$159.6682	$159.67	$159.65	$159.70
Purchase #2	$193.66	5.512%	$204.3345	$204.33	$204.35	$204.30
Purchase #3	$34.90	7.608%	$37.5552	$37.56	$37.55	$37.60
Purchase #4	$103.25	10.451%	$114.0407	$114.04	$114.05	$114.00
Purchase #5	$50.93	6.676%	$54.3301	$54.33	$54.35	$54.30
Purchase #6	$18.54	13.844%	$21.1067	$21.11	$21.10	$21.10
Purchase #7	$9.56	12.721%	$10.7761	$10.78	$10.80	$10.80
7 purchase totals =	$551.79		$601.8115	$601.82	$601.85	$601.80