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	$41.72	8.491%	$45.2624	$45.26	$45.25	$45.30
Purchase #2	$33.52	6.784%	$35.794	$35.79	$35.80	$35.80
Purchase #3	$163.50	5.443%	$172.3993	$172.40	$172.40	$172.40
Purchase #4	$86.48	4.337%	$90.2306	$90.23	$90.25	$90.20
Purchase #5	$25.36	9.603%	$27.7953	$27.80	$27.80	$27.80
Purchase #6	$224.40	4.149%	$233.7104	$233.71	$233.70	$233.70
Purchase #7	$45.35	4.710%	$47.486	$47.49	$47.50	$47.50
7 purchase totals =	$620.33		$652.6780	$652.68	$652.70	$652.70