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	$178.31	10.611%	$197.2305	$197.23	$197.25	$197.20
Purchase #2	$76.78	11.149%	$85.3402	$85.34	$85.35	$85.30
Purchase #3	$75.86	4.352%	$79.1614	$79.16	$79.15	$79.20
Purchase #4	$101.85	12.195%	$114.2706	$114.27	$114.25	$114.30
Purchase #5	$150.45	3.445%	$155.633	$155.63	$155.65	$155.60
Purchase #6	$14.59	5.854%	$15.4441	$15.44	$15.45	$15.40
Purchase #7	$82.58	10.815%	$91.511	$91.51	$91.50	$91.50
7 purchase totals =	$680.42		$738.5908	$738.58	$738.60	$738.50