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	$67.41	10.572%	$74.5366	$74.54	$74.55	$74.50
Purchase #2	$12.91	12.345%	$14.5037	$14.50	$14.50	$14.50
Purchase #3	$34.71	13.778%	$39.4923	$39.49	$39.50	$39.50
Purchase #4	$111.67	10.723%	$123.6444	$123.64	$123.65	$123.60
Purchase #5	$78.82	4.208%	$82.1367	$82.14	$82.15	$82.10
Purchase #6	$101.82	13.764%	$115.8345	$115.83	$115.85	$115.80
Purchase #7	$204.96	13.521%	$232.6726	$232.67	$232.65	$232.70
7 purchase totals =	$612.30		$682.8208	$682.81	$682.85	$682.70