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	$128.86	13.624%	$146.4159	$146.42	$146.40	$146.40
Purchase #2	$218.81	13.743%	$248.8811	$248.88	$248.90	$248.90
Purchase #3	$225.58	5.416%	$237.7974	$237.80	$237.80	$237.80
Purchase #4	$95.62	10.675%	$105.8274	$105.83	$105.85	$105.80
Purchase #5	$69.72	13.823%	$79.3574	$79.36	$79.35	$79.40
Purchase #6	$140.52	4.280%	$146.5343	$146.53	$146.55	$146.50
Purchase #7	$139.31	5.331%	$146.7366	$146.74	$146.75	$146.70
7 purchase totals =	$1,018.42		$1,111.5501	$1,111.56	$1,111.60	$1,111.50