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	$60.73	11.135%	$67.4923	$67.49	$67.50	$67.50
Purchase #2	$27.80	11.618%	$31.0298	$31.03	$31.05	$31.00
Purchase #3	$123.50	6.321%	$131.3064	$131.31	$131.30	$131.30
Purchase #4	$214.74	11.118%	$238.6148	$238.61	$238.60	$238.60
Purchase #5	$61.39	8.394%	$66.5431	$66.54	$66.55	$66.50
Purchase #6	$32.45	11.504%	$36.183	$36.18	$36.20	$36.20
Purchase #7	$224.95	12.251%	$252.5086	$252.51	$252.50	$252.50
7 purchase totals =	$745.56		$823.6780	$823.67	$823.70	$823.60