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	$208.74	10.571%	$230.8059	$230.81	$230.80	$230.80
Purchase #2	$154.86	4.556%	$161.9154	$161.92	$161.90	$161.90
Purchase #3	$41.62	11.752%	$46.5112	$46.51	$46.50	$46.50
Purchase #4	$35.88	13.712%	$40.7999	$40.80	$40.80	$40.80
Purchase #5	$211.60	8.593%	$229.7828	$229.78	$229.80	$229.80
Purchase #6	$112.51	13.363%	$127.5447	$127.54	$127.55	$127.50
Purchase #7	$192.67	8.751%	$209.5306	$209.53	$209.55	$209.50
7 purchase totals =	$957.88		$1,046.8905	$1,046.89	$1,046.90	$1,046.80