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	$212.29	10.169%	$233.8778	$233.88	$233.90	$233.90
Purchase #2	$218.92	10.781%	$242.5218	$242.52	$242.50	$242.50
Purchase #3	$115.90	4.127%	$120.6832	$120.68	$120.70	$120.70
Purchase #4	$42.93	5.108%	$45.1229	$45.12	$45.10	$45.10
Purchase #5	$44.57	11.272%	$49.5939	$49.59	$49.60	$49.60
Purchase #6	$215.57	5.518%	$227.4652	$227.47	$227.45	$227.50
Purchase #7	$59.94	8.740%	$65.1788	$65.18	$65.20	$65.20
7 purchase totals =	$910.12		$984.4436	$984.44	$984.45	$984.50