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	$155.58	7.240%	$166.844	$166.84	$166.85	$166.80
Purchase #2	$184.33	4.435%	$192.505	$192.51	$192.50	$192.50
Purchase #3	$238.66	6.504%	$254.1824	$254.18	$254.20	$254.20
Purchase #4	$62.25	8.529%	$67.5593	$67.56	$67.55	$67.60
Purchase #5	$108.72	8.131%	$117.56	$117.56	$117.55	$117.60
Purchase #6	$50.68	7.426%	$54.4435	$54.44	$54.45	$54.40
Purchase #7	$69.31	13.671%	$78.7854	$78.79	$78.80	$78.80
7 purchase totals =	$869.53		$931.8796	$931.88	$931.90	$931.90