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	$236.59	7.600%	$254.5708	$254.57	$254.55	$254.60
Purchase #2	$178.41	7.570%	$191.9156	$191.92	$191.90	$191.90
Purchase #3	$58.69	9.199%	$64.0889	$64.09	$64.10	$64.10
Purchase #4	$139.85	4.176%	$145.6901	$145.69	$145.70	$145.70
Purchase #5	$89.62	10.397%	$98.9378	$98.94	$98.95	$98.90
Purchase #6	$49.78	5.695%	$52.615	$52.62	$52.60	$52.60
Purchase #7	$199.95	12.725%	$225.3936	$225.39	$225.40	$225.40
7 purchase totals =	$952.89		$1,033.2118	$1,033.22	$1,033.20	$1,033.20