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	$64.77	10.199%	$71.3759	$71.38	$71.40	$71.40
Purchase #2	$218.88	9.332%	$239.3059	$239.31	$239.30	$239.30
Purchase #3	$138.40	13.686%	$157.3414	$157.34	$157.35	$157.30
Purchase #4	$169.68	5.527%	$179.0582	$179.06	$179.05	$179.10
Purchase #5	$40.79	4.406%	$42.5872	$42.59	$42.60	$42.60
Purchase #6	$18.27	10.788%	$20.241	$20.24	$20.25	$20.20
Purchase #7	$238.92	4.778%	$250.3356	$250.34	$250.35	$250.30
7 purchase totals =	$889.71		$960.2452	$960.26	$960.30	$960.20