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	$202.27	3.569%	$209.489	$209.49	$209.50	$209.50
Purchase #2	$155.35	3.378%	$160.5977	$160.60	$160.60	$160.60
Purchase #3	$70.75	10.487%	$78.1696	$78.17	$78.15	$78.20
Purchase #4	$97.83	7.727%	$105.3893	$105.39	$105.40	$105.40
Purchase #5	$150.44	3.321%	$155.4361	$155.44	$155.45	$155.40
Purchase #6	$117.33	12.628%	$132.1464	$132.15	$132.15	$132.10
Purchase #7	$170.53	11.853%	$190.7429	$190.74	$190.75	$190.70
7 purchase totals =	$964.50		$1,031.9710	$1,031.98	$1,032.00	$1,031.90