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	$54.83	8.418%	$59.4456	$59.45	$59.45	$59.40
Purchase #2	$74.60	5.131%	$78.4277	$78.43	$78.45	$78.40
Purchase #3	$6.66	11.537%	$7.4284	$7.43	$7.45	$7.40
Purchase #4	$195.60	10.464%	$216.0676	$216.07	$216.05	$216.10
Purchase #5	$241.76	8.736%	$262.8802	$262.88	$262.90	$262.90
Purchase #6	$16.44	8.151%	$17.78	$17.78	$17.80	$17.80
Purchase #7	$51.71	10.437%	$57.107	$57.11	$57.10	$57.10
7 purchase totals =	$641.60		$699.1365	$699.15	$699.20	$699.10