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	$136.63	12.149%	$153.2292	$153.23	$153.25	$153.20
Purchase #2	$205.46	12.798%	$231.7548	$231.75	$231.75	$231.80
Purchase #3	$144.96	4.707%	$151.7833	$151.78	$151.80	$151.80
Purchase #4	$132.57	11.464%	$147.7678	$147.77	$147.75	$147.80
Purchase #5	$174.92	3.796%	$181.56	$181.56	$181.55	$181.60
Purchase #6	$158.74	10.798%	$175.8807	$175.88	$175.90	$175.90
Purchase #7	$147.49	4.674%	$154.3837	$154.38	$154.40	$154.40
7 purchase totals =	$1,100.77		$1,196.3595	$1,196.35	$1,196.40	$1,196.50