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	$227.38	8.757%	$247.2917	$247.29	$247.30	$247.30
Purchase #2	$56.32	5.563%	$59.4531	$59.45	$59.45	$59.50
Purchase #3	$125.26	10.285%	$138.143	$138.14	$138.15	$138.10
Purchase #4	$104.66	7.796%	$112.8193	$112.82	$112.80	$112.80
Purchase #5	$18.28	3.479%	$18.916	$18.92	$18.90	$18.90
Purchase #6	$221.27	9.180%	$241.5826	$241.58	$241.60	$241.60
Purchase #7	$82.81	7.311%	$88.8642	$88.86	$88.85	$88.90
7 purchase totals =	$835.98		$907.0699	$907.06	$907.05	$907.10