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	$152.46	6.307%	$162.0757	$162.08	$162.10	$162.10
Purchase #2	$28.53	13.142%	$32.2794	$32.28	$32.30	$32.30
Purchase #3	$103.30	7.544%	$111.093	$111.09	$111.10	$111.10
Purchase #4	$218.25	6.190%	$231.7597	$231.76	$231.75	$231.80
Purchase #5	$18.31	5.457%	$19.3092	$19.31	$19.30	$19.30
Purchase #6	$81.86	3.297%	$84.5589	$84.56	$84.55	$84.60
Purchase #7	$107.68	7.808%	$116.0877	$116.09	$116.10	$116.10
7 purchase totals =	$710.39		$757.1636	$757.17	$757.20	$757.30