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	$130.34	10.220%	$143.6607	$143.66	$143.65	$143.70
Purchase #2	$73.31	9.267%	$80.1036	$80.10	$80.10	$80.10
Purchase #3	$142.39	10.679%	$157.5958	$157.60	$157.60	$157.60
Purchase #4	$92.49	13.597%	$105.0659	$105.07	$105.05	$105.10
Purchase #5	$157.41	11.820%	$176.0159	$176.02	$176.00	$176.00
Purchase #6	$82.52	8.792%	$89.7752	$89.78	$89.80	$89.80
Purchase #7	$84.58	13.674%	$96.1455	$96.15	$96.15	$96.10
7 purchase totals =	$763.04		$848.3626	$848.38	$848.35	$848.40