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	$184.86	8.458%	$200.4955	$200.50	$200.50	$200.50
Purchase #2	$116.29	4.578%	$121.6138	$121.61	$121.60	$121.60
Purchase #3	$12.89	7.753%	$13.8894	$13.89	$13.90	$13.90
Purchase #4	$232.42	10.368%	$256.5173	$256.52	$256.50	$256.50
Purchase #5	$80.98	11.113%	$89.9793	$89.98	$90.00	$90.00
Purchase #6	$105.99	9.127%	$115.6637	$115.66	$115.65	$115.70
Purchase #7	$134.55	9.286%	$147.0443	$147.04	$147.05	$147.00
7 purchase totals =	$867.98		$945.2033	$945.20	$945.20	$945.20