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	$126.65	13.132%	$143.2817	$143.28	$143.30	$143.30
Purchase #2	$154.29	8.626%	$167.5991	$167.60	$167.60	$167.60
Purchase #3	$34.54	8.817%	$37.5854	$37.59	$37.60	$37.60
Purchase #4	$242.71	3.462%	$251.1126	$251.11	$251.10	$251.10
Purchase #5	$217.33	11.291%	$241.8687	$241.87	$241.85	$241.90
Purchase #6	$31.61	3.525%	$32.7243	$32.72	$32.70	$32.70
Purchase #7	$189.54	8.296%	$205.2642	$205.26	$205.25	$205.30
7 purchase totals =	$996.67		$1,079.4360	$1,079.43	$1,079.40	$1,079.50