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	$56.99	9.278%	$62.2775	$62.28	$62.30	$62.30
Purchase #2	$113.57	13.165%	$128.5215	$128.52	$128.50	$128.50
Purchase #3	$85.90	6.512%	$91.4938	$91.49	$91.50	$91.50
Purchase #4	$224.86	7.813%	$242.4283	$242.43	$242.45	$242.40
Purchase #5	$152.47	13.239%	$172.6555	$172.66	$172.65	$172.70
Purchase #6	$139.86	7.559%	$150.432	$150.43	$150.45	$150.40
Purchase #7	$35.98	8.844%	$39.1621	$39.16	$39.15	$39.20
7 purchase totals =	$809.63		$886.9707	$886.97	$887.00	$887.00