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	$73.83	11.672%	$82.4474	$82.45	$82.45	$82.40
Purchase #2	$48.47	3.271%	$50.0555	$50.06	$50.05	$50.10
Purchase #3	$96.60	5.561%	$101.9719	$101.97	$101.95	$102.00
Purchase #4	$17.79	13.380%	$20.1703	$20.17	$20.15	$20.20
Purchase #5	$69.39	13.276%	$78.6022	$78.60	$78.60	$78.60
Purchase #6	$238.75	7.551%	$256.778	$256.78	$256.80	$256.80
Purchase #7	$150.51	12.870%	$169.8806	$169.88	$169.90	$169.90
7 purchase totals =	$695.34		$759.9059	$759.91	$759.90	$760.00