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	$149.59	8.778%	$162.721	$162.72	$162.70	$162.70
Purchase #2	$135.60	4.746%	$142.0356	$142.04	$142.05	$142.00
Purchase #3	$120.60	5.593%	$127.3452	$127.35	$127.35	$127.30
Purchase #4	$112.49	7.356%	$120.7648	$120.76	$120.75	$120.80
Purchase #5	$248.38	12.250%	$278.8066	$278.81	$278.80	$278.80
Purchase #6	$117.41	5.771%	$124.1857	$124.19	$124.20	$124.20
Purchase #7	$119.49	9.143%	$130.415	$130.42	$130.40	$130.40
7 purchase totals =	$1,003.56		$1,086.2739	$1,086.29	$1,086.25	$1,086.20