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	$193.95	3.147%	$200.0536	$200.05	$200.05	$200.10
Purchase #2	$227.86	10.476%	$251.7306	$251.73	$251.75	$251.70
Purchase #3	$62.44	13.633%	$70.9524	$70.95	$70.95	$71.00
Purchase #4	$45.25	13.321%	$51.2778	$51.28	$51.30	$51.30
Purchase #5	$18.43	10.168%	$20.304	$20.30	$20.30	$20.30
Purchase #6	$42.32	7.741%	$45.596	$45.60	$45.60	$45.60
Purchase #7	$87.29	12.545%	$98.2405	$98.24	$98.25	$98.20
7 purchase totals =	$677.54		$738.1549	$738.15	$738.20	$738.20