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	$164.30	11.626%	$183.4015	$183.40	$183.40	$183.40
Purchase #2	$141.76	11.565%	$158.1545	$158.15	$158.15	$158.20
Purchase #3	$173.59	10.178%	$191.258	$191.26	$191.25	$191.30
Purchase #4	$148.47	7.727%	$159.9423	$159.94	$159.95	$159.90
Purchase #5	$122.48	4.650%	$128.1753	$128.18	$128.20	$128.20
Purchase #6	$158.73	10.248%	$174.9967	$175.00	$175.00	$175.00
Purchase #7	$75.53	13.377%	$85.6336	$85.63	$85.65	$85.60
7 purchase totals =	$984.86		$1,081.5619	$1,081.56	$1,081.60	$1,081.60