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	$93.60	8.465%	$101.5232	$101.52	$101.50	$101.50
Purchase #2	$61.92	4.118%	$64.4699	$64.47	$64.45	$64.50
Purchase #3	$64.60	3.390%	$66.7899	$66.79	$66.80	$66.80
Purchase #4	$23.46	7.467%	$25.2118	$25.21	$25.20	$25.20
Purchase #5	$96.84	12.809%	$109.2442	$109.24	$109.25	$109.20
Purchase #6	$64.76	11.748%	$72.368	$72.37	$72.35	$72.40
Purchase #7	$123.56	11.473%	$137.736	$137.74	$137.75	$137.70
7 purchase totals =	$528.74		$577.3430	$577.34	$577.30	$577.30