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	$135.27	11.376%	$150.6583	$150.66	$150.65	$150.70
Purchase #2	$89.46	11.159%	$99.4428	$99.44	$99.45	$99.40
Purchase #3	$60.86	3.227%	$62.824	$62.82	$62.80	$62.80
Purchase #4	$153.79	3.663%	$159.4233	$159.42	$159.40	$159.40
Purchase #5	$238.46	7.167%	$255.5504	$255.55	$255.55	$255.60
Purchase #6	$95.84	9.829%	$105.2601	$105.26	$105.25	$105.30
Purchase #7	$80.55	7.378%	$86.493	$86.49	$86.50	$86.50
7 purchase totals =	$854.23		$919.6519	$919.64	$919.60	$919.70