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	$233.68	4.382%	$243.9199	$243.92	$243.90	$243.90
Purchase #2	$145.47	5.778%	$153.8753	$153.88	$153.90	$153.90
Purchase #3	$71.90	9.255%	$78.5543	$78.55	$78.55	$78.60
Purchase #4	$72.42	8.472%	$78.5554	$78.56	$78.55	$78.60
Purchase #5	$189.99	8.558%	$206.2493	$206.25	$206.25	$206.20
Purchase #6	$70.51	8.859%	$76.7565	$76.76	$76.75	$76.80
Purchase #7	$235.53	12.732%	$265.5177	$265.52	$265.50	$265.50
7 purchase totals =	$1,019.50		$1,103.4284	$1,103.44	$1,103.40	$1,103.50