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	$40.81	11.223%	$45.3901	$45.39	$45.40	$45.40
Purchase #2	$218.77	12.600%	$246.335	$246.34	$246.35	$246.30
Purchase #3	$105.59	12.132%	$118.4002	$118.40	$118.40	$118.40
Purchase #4	$127.83	13.608%	$145.2251	$145.23	$145.25	$145.20
Purchase #5	$131.63	12.671%	$148.3088	$148.31	$148.30	$148.30
Purchase #6	$177.37	10.828%	$196.5756	$196.58	$196.60	$196.60
Purchase #7	$84.45	11.619%	$94.2622	$94.26	$94.25	$94.30
7 purchase totals =	$886.45		$994.4970	$994.51	$994.55	$994.50