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	$233.95	5.601%	$247.0535	$247.05	$247.05	$247.10
Purchase #2	$48.36	9.699%	$53.0504	$53.05	$53.05	$53.10
Purchase #3	$85.38	6.458%	$90.8938	$90.89	$90.90	$90.90
Purchase #4	$200.69	3.229%	$207.1703	$207.17	$207.15	$207.20
Purchase #5	$248.84	4.594%	$260.2717	$260.27	$260.25	$260.30
Purchase #6	$44.47	7.281%	$47.7079	$47.71	$47.70	$47.70
Purchase #7	$102.71	6.604%	$109.493	$109.49	$109.50	$109.50
7 purchase totals =	$964.40		$1,015.6406	$1,015.63	$1,015.60	$1,015.80