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	$60.33	13.599%	$68.5343	$68.53	$68.55	$68.50
Purchase #2	$72.61	7.171%	$77.8169	$77.82	$77.80	$77.80
Purchase #3	$19.33	3.861%	$20.0763	$20.08	$20.10	$20.10
Purchase #4	$231.35	4.432%	$241.6034	$241.60	$241.60	$241.60
Purchase #5	$139.50	9.514%	$152.772	$152.77	$152.75	$152.80
Purchase #6	$91.91	13.176%	$104.0201	$104.02	$104.00	$104.00
Purchase #7	$55.71	10.436%	$61.5239	$61.52	$61.50	$61.50
7 purchase totals =	$670.74		$726.3469	$726.34	$726.30	$726.30