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	$90.99	13.685%	$103.442	$103.44	$103.45	$103.40
Purchase #2	$90.91	13.547%	$103.2256	$103.23	$103.25	$103.20
Purchase #3	$7.58	6.792%	$8.0948	$8.09	$8.10	$8.10
Purchase #4	$212.35	7.226%	$227.6944	$227.69	$227.70	$227.70
Purchase #5	$39.25	8.369%	$42.5348	$42.53	$42.55	$42.50
Purchase #6	$53.91	9.786%	$59.1856	$59.19	$59.20	$59.20
Purchase #7	$120.37	11.605%	$134.3389	$134.34	$134.35	$134.30
7 purchase totals =	$615.36		$678.5161	$678.51	$678.60	$678.40