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	$147.67	3.514%	$152.8591	$152.86	$152.85	$152.90
Purchase #2	$217.73	9.673%	$238.791	$238.79	$238.80	$238.80
Purchase #3	$34.31	9.370%	$37.5248	$37.52	$37.50	$37.50
Purchase #4	$138.60	10.193%	$152.7275	$152.73	$152.75	$152.70
Purchase #5	$149.37	5.665%	$157.8318	$157.83	$157.85	$157.80
Purchase #6	$237.66	10.721%	$263.1395	$263.14	$263.15	$263.10
Purchase #7	$172.91	3.800%	$179.4806	$179.48	$179.50	$179.50
7 purchase totals =	$1,098.25		$1,182.3543	$1,182.35	$1,182.40	$1,182.30