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	$10.48	4.176%	$10.9176	$10.92	$10.90	$10.90
Purchase #2	$237.89	3.781%	$246.8846	$246.88	$246.90	$246.90
Purchase #3	$244.76	13.799%	$278.5344	$278.53	$278.55	$278.50
Purchase #4	$130.86	10.508%	$144.6108	$144.61	$144.60	$144.60
Purchase #5	$98.54	7.766%	$106.1926	$106.19	$106.20	$106.20
Purchase #6	$161.60	6.724%	$172.466	$172.47	$172.45	$172.50
Purchase #7	$88.40	3.670%	$91.6443	$91.64	$91.65	$91.60
7 purchase totals =	$972.53		$1,051.2503	$1,051.24	$1,051.25	$1,051.20