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	$60.76	11.570%	$67.7899	$67.79	$67.80	$67.80
Purchase #2	$133.75	7.724%	$144.0809	$144.08	$144.10	$144.10
Purchase #3	$249.79	4.858%	$261.9248	$261.92	$261.90	$261.90
Purchase #4	$49.27	8.821%	$53.6161	$53.62	$53.60	$53.60
Purchase #5	$16.67	7.142%	$17.8606	$17.86	$17.85	$17.90
Purchase #6	$33.28	7.849%	$35.8921	$35.89	$35.90	$35.90
Purchase #7	$83.30	10.383%	$91.949	$91.95	$91.95	$91.90
7 purchase totals =	$626.82		$673.1134	$673.11	$673.10	$673.10