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	$243.90	7.215%	$261.4974	$261.50	$261.50	$261.50
Purchase #2	$243.28	6.295%	$258.5945	$258.59	$258.60	$258.60
Purchase #3	$110.70	5.419%	$116.6988	$116.70	$116.70	$116.70
Purchase #4	$143.76	6.251%	$152.7464	$152.75	$152.75	$152.70
Purchase #5	$206.90	11.394%	$230.4742	$230.47	$230.45	$230.50
Purchase #6	$128.53	13.105%	$145.3739	$145.37	$145.35	$145.40
Purchase #7	$204.31	8.728%	$222.1422	$222.14	$222.15	$222.10
7 purchase totals =	$1,281.38		$1,387.5274	$1,387.52	$1,387.50	$1,387.50