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	$118.62	7.754%	$127.8178	$127.82	$127.80	$127.80
Purchase #2	$207.80	4.865%	$217.9095	$217.91	$217.90	$217.90
Purchase #3	$166.58	5.822%	$176.2783	$176.28	$176.30	$176.30
Purchase #4	$120.98	11.432%	$134.8104	$134.81	$134.80	$134.80
Purchase #5	$34.61	9.107%	$37.7619	$37.76	$37.75	$37.80
Purchase #6	$104.70	13.552%	$118.8889	$118.89	$118.90	$118.90
Purchase #7	$76.71	10.852%	$85.0346	$85.03	$85.05	$85.00
7 purchase totals =	$830.00		$898.5014	$898.50	$898.50	$898.50