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	$206.41	11.720%	$230.6013	$230.60	$230.60	$230.60
Purchase #2	$188.90	4.134%	$196.7091	$196.71	$196.70	$196.70
Purchase #3	$218.25	6.766%	$233.0168	$233.02	$233.00	$233.00
Purchase #4	$113.95	11.775%	$127.3676	$127.37	$127.35	$127.40
Purchase #5	$75.43	11.277%	$83.9362	$83.94	$83.95	$83.90
Purchase #6	$99.83	5.628%	$105.4484	$105.45	$105.45	$105.40
Purchase #7	$170.50	4.766%	$178.626	$178.63	$178.65	$178.60
7 purchase totals =	$1,073.27		$1,155.7054	$1,155.72	$1,155.70	$1,155.60