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	$155.38	7.852%	$167.5804	$167.58	$167.60	$167.60
Purchase #2	$44.42	3.800%	$46.108	$46.11	$46.10	$46.10
Purchase #3	$144.62	12.370%	$162.5095	$162.51	$162.50	$162.50
Purchase #4	$81.30	12.861%	$91.756	$91.76	$91.75	$91.80
Purchase #5	$215.71	8.187%	$233.3702	$233.37	$233.35	$233.40
Purchase #6	$141.92	13.371%	$160.8961	$160.90	$160.90	$160.90
Purchase #7	$49.46	9.737%	$54.2759	$54.28	$54.30	$54.30
7 purchase totals =	$832.81		$916.4961	$916.51	$916.50	$916.60