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	$143.69	13.222%	$162.6887	$162.69	$162.70	$162.70
Purchase #2	$144.50	11.137%	$160.593	$160.59	$160.60	$160.60
Purchase #3	$151.38	11.323%	$168.5208	$168.52	$168.50	$168.50
Purchase #4	$122.66	11.279%	$136.4948	$136.49	$136.50	$136.50
Purchase #5	$58.97	6.462%	$62.7806	$62.78	$62.80	$62.80
Purchase #6	$16.39	11.284%	$18.2394	$18.24	$18.25	$18.20
Purchase #7	$22.53	13.682%	$25.6126	$25.61	$25.60	$25.60
7 purchase totals =	$660.12		$734.9299	$734.92	$734.95	$734.90