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	$205.41	11.626%	$229.291	$229.29	$229.30	$229.30
Purchase #2	$106.61	9.127%	$116.3403	$116.34	$116.35	$116.30
Purchase #3	$87.80	5.344%	$92.492	$92.49	$92.50	$92.50
Purchase #4	$68.81	4.157%	$71.6704	$71.67	$71.65	$71.70
Purchase #5	$161.86	9.259%	$176.8466	$176.85	$176.85	$176.80
Purchase #6	$14.94	3.465%	$15.4577	$15.46	$15.45	$15.50
Purchase #7	$59.86	9.447%	$65.515	$65.52	$65.50	$65.50
7 purchase totals =	$705.29		$767.6130	$767.62	$767.60	$767.60