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	$42.35	3.783%	$43.9521	$43.95	$43.95	$44.00
Purchase #2	$86.33	5.240%	$90.8537	$90.85	$90.85	$90.90
Purchase #3	$81.77	4.636%	$85.5609	$85.56	$85.55	$85.60
Purchase #4	$96.67	8.384%	$104.7748	$104.77	$104.75	$104.80
Purchase #5	$107.28	3.371%	$110.8964	$110.90	$110.90	$110.90
Purchase #6	$155.69	10.619%	$172.2227	$172.22	$172.20	$172.20
Purchase #7	$46.32	6.464%	$49.3141	$49.31	$49.30	$49.30
7 purchase totals =	$616.41		$657.5747	$657.56	$657.50	$657.70