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	$172.81	13.150%	$195.5345	$195.53	$195.55	$195.50
Purchase #2	$148.45	5.485%	$156.5925	$156.59	$156.60	$156.60
Purchase #3	$45.54	12.478%	$51.2225	$51.22	$51.20	$51.20
Purchase #4	$235.88	8.467%	$255.852	$255.85	$255.85	$255.90
Purchase #5	$193.64	8.517%	$210.1323	$210.13	$210.15	$210.10
Purchase #6	$112.88	12.872%	$127.4099	$127.41	$127.40	$127.40
Purchase #7	$43.58	6.656%	$46.4807	$46.48	$46.50	$46.50
7 purchase totals =	$952.78		$1,043.2244	$1,043.21	$1,043.25	$1,043.20