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	$219.81	9.750%	$241.2415	$241.24	$241.25	$241.20
Purchase #2	$115.78	13.259%	$131.1313	$131.13	$131.15	$131.10
Purchase #3	$234.72	3.460%	$242.8413	$242.84	$242.85	$242.80
Purchase #4	$167.58	13.585%	$190.3457	$190.35	$190.35	$190.30
Purchase #5	$202.54	9.798%	$222.3849	$222.38	$222.40	$222.40
Purchase #6	$30.35	9.182%	$33.1367	$33.14	$33.15	$33.10
Purchase #7	$11.90	3.174%	$12.2777	$12.28	$12.30	$12.30
7 purchase totals =	$982.68		$1,073.3591	$1,073.36	$1,073.45	$1,073.20