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	$64.64	10.258%	$71.2708	$71.27	$71.25	$71.30
Purchase #2	$212.62	8.606%	$230.9181	$230.92	$230.90	$230.90
Purchase #3	$83.90	3.478%	$86.818	$86.82	$86.80	$86.80
Purchase #4	$74.67	5.563%	$78.8239	$78.82	$78.80	$78.80
Purchase #5	$138.55	3.278%	$143.0917	$143.09	$143.10	$143.10
Purchase #6	$58.53	6.465%	$62.314	$62.31	$62.30	$62.30
Purchase #7	$192.73	12.576%	$216.9677	$216.97	$216.95	$217.00
7 purchase totals =	$825.64		$890.2042	$890.20	$890.10	$890.20