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	$166.60	11.143%	$185.1642	$185.16	$185.15	$185.20
Purchase #2	$93.37	6.813%	$99.7313	$99.73	$99.75	$99.70
Purchase #3	$11.63	3.223%	$12.0048	$12.00	$12.00	$12.00
Purchase #4	$208.77	13.740%	$237.455	$237.46	$237.45	$237.50
Purchase #5	$192.72	10.311%	$212.5914	$212.59	$212.60	$212.60
Purchase #6	$74.78	10.481%	$82.6177	$82.62	$82.60	$82.60
Purchase #7	$29.29	4.104%	$30.4921	$30.49	$30.50	$30.50
7 purchase totals =	$777.16		$860.0565	$860.05	$860.05	$860.10