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	$112.82	4.535%	$117.9364	$117.94	$117.95	$117.90
Purchase #2	$81.71	5.538%	$86.2351	$86.24	$86.25	$86.20
Purchase #3	$165.63	4.223%	$172.6246	$172.62	$172.60	$172.60
Purchase #4	$46.25	8.688%	$50.2682	$50.27	$50.25	$50.30
Purchase #5	$176.79	8.117%	$191.14	$191.14	$191.15	$191.10
Purchase #6	$17.25	12.753%	$19.4499	$19.45	$19.45	$19.40
Purchase #7	$154.45	10.626%	$170.8619	$170.86	$170.85	$170.90
7 purchase totals =	$754.90		$808.5161	$808.52	$808.50	$808.40