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	$105.62	6.606%	$112.5973	$112.60	$112.60	$112.60
Purchase #2	$38.73	10.203%	$42.6816	$42.68	$42.70	$42.70
Purchase #3	$215.42	8.567%	$233.875	$233.88	$233.90	$233.90
Purchase #4	$81.86	11.242%	$91.0627	$91.06	$91.05	$91.10
Purchase #5	$20.78	6.669%	$22.1658	$22.17	$22.15	$22.20
Purchase #6	$95.78	3.565%	$99.1946	$99.19	$99.20	$99.20
Purchase #7	$87.33	13.646%	$99.2471	$99.25	$99.25	$99.20
7 purchase totals =	$645.52		$700.8241	$700.83	$700.85	$700.90