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	$178.33	6.758%	$190.3815	$190.38	$190.40	$190.40
Purchase #2	$48.62	8.256%	$52.6341	$52.63	$52.65	$52.60
Purchase #3	$51.80	12.251%	$58.146	$58.15	$58.15	$58.10
Purchase #4	$12.64	5.443%	$13.328	$13.33	$13.35	$13.30
Purchase #5	$38.89	5.151%	$40.8932	$40.89	$40.90	$40.90
Purchase #6	$22.49	7.627%	$24.2053	$24.21	$24.20	$24.20
Purchase #7	$19.62	11.328%	$21.8426	$21.84	$21.85	$21.80
7 purchase totals =	$372.39		$401.4307	$401.43	$401.50	$401.30