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	$200.59	10.345%	$221.341	$221.34	$221.35	$221.30
Purchase #2	$63.63	9.847%	$69.8956	$69.90	$69.90	$69.90
Purchase #3	$196.77	13.185%	$222.7141	$222.71	$222.70	$222.70
Purchase #4	$62.30	13.604%	$70.7753	$70.78	$70.80	$70.80
Purchase #5	$202.80	4.493%	$211.9118	$211.91	$211.90	$211.90
Purchase #6	$118.60	4.797%	$124.2892	$124.29	$124.30	$124.30
Purchase #7	$105.35	12.852%	$118.8896	$118.89	$118.90	$118.90
7 purchase totals =	$950.04		$1,039.8166	$1,039.82	$1,039.85	$1,039.80