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	$93.62	12.760%	$105.5659	$105.57	$105.55	$105.60
Purchase #2	$81.64	7.344%	$87.6356	$87.64	$87.65	$87.60
Purchase #3	$134.61	13.805%	$153.1929	$153.19	$153.20	$153.20
Purchase #4	$67.89	10.664%	$75.1298	$75.13	$75.15	$75.10
Purchase #5	$143.91	4.328%	$150.1384	$150.14	$150.15	$150.10
Purchase #6	$90.97	10.128%	$100.1834	$100.18	$100.20	$100.20
Purchase #7	$100.34	3.109%	$103.4596	$103.46	$103.45	$103.50
7 purchase totals =	$712.98		$775.3056	$775.31	$775.35	$775.30