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	$54.39	4.390%	$56.7777	$56.78	$56.80	$56.80
Purchase #2	$54.28	6.717%	$57.926	$57.93	$57.95	$57.90
Purchase #3	$18.77	11.398%	$20.9094	$20.91	$20.90	$20.90
Purchase #4	$186.91	13.211%	$211.6027	$211.60	$211.60	$211.60
Purchase #5	$209.30	10.739%	$231.7767	$231.78	$231.80	$231.80
Purchase #6	$230.85	3.264%	$238.3849	$238.38	$238.40	$238.40
Purchase #7	$246.84	6.156%	$262.0355	$262.04	$262.05	$262.00
7 purchase totals =	$1,001.34		$1,079.4129	$1,079.42	$1,079.50	$1,079.40