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	$87.91	7.635%	$94.6219	$94.62	$94.60	$94.60
Purchase #2	$79.67	11.824%	$89.0902	$89.09	$89.10	$89.10
Purchase #3	$107.55	10.475%	$118.8159	$118.82	$118.80	$118.80
Purchase #4	$73.38	7.850%	$79.1403	$79.14	$79.15	$79.10
Purchase #5	$132.32	7.588%	$142.3604	$142.36	$142.35	$142.40
Purchase #6	$81.70	11.256%	$90.8962	$90.90	$90.90	$90.90
Purchase #7	$28.87	12.554%	$32.4943	$32.49	$32.50	$32.50
7 purchase totals =	$591.40		$647.4192	$647.42	$647.40	$647.40