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	$164.96	11.816%	$184.4517	$184.45	$184.45	$184.50
Purchase #2	$10.76	13.848%	$12.25	$12.25	$12.25	$12.30
Purchase #3	$87.65	13.563%	$99.538	$99.54	$99.55	$99.50
Purchase #4	$90.48	4.874%	$94.89	$94.89	$94.90	$94.90
Purchase #5	$205.73	6.525%	$219.1539	$219.15	$219.15	$219.20
Purchase #6	$205.93	10.599%	$227.7565	$227.76	$227.75	$227.80
Purchase #7	$145.83	11.328%	$162.3496	$162.35	$162.35	$162.30
7 purchase totals =	$911.34		$1,000.3897	$1,000.39	$1,000.40	$1,000.50