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	$214.84	12.505%	$241.7057	$241.71	$241.70	$241.70
Purchase #2	$100.64	10.713%	$111.4216	$111.42	$111.40	$111.40
Purchase #3	$195.45	4.606%	$204.4524	$204.45	$204.45	$204.50
Purchase #4	$187.42	12.481%	$210.8119	$210.81	$210.80	$210.80
Purchase #5	$29.34	6.822%	$31.3416	$31.34	$31.35	$31.30
Purchase #6	$141.28	13.117%	$159.8117	$159.81	$159.80	$159.80
Purchase #7	$172.71	13.850%	$196.6303	$196.63	$196.65	$196.60
7 purchase totals =	$1,041.68		$1,156.1752	$1,156.17	$1,156.15	$1,156.10