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	$156.82	10.678%	$173.5652	$173.57	$173.55	$173.60
Purchase #2	$112.29	5.334%	$118.2795	$118.28	$118.30	$118.30
Purchase #3	$222.83	9.317%	$243.5911	$243.59	$243.60	$243.60
Purchase #4	$99.87	10.618%	$110.4742	$110.47	$110.45	$110.50
Purchase #5	$10.75	10.576%	$11.8869	$11.89	$11.90	$11.90
Purchase #6	$185.64	10.860%	$205.8005	$205.80	$205.80	$205.80
Purchase #7	$82.38	12.571%	$92.736	$92.74	$92.75	$92.70
7 purchase totals =	$870.58		$956.3334	$956.34	$956.35	$956.40