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	$185.95	13.390%	$210.8487	$210.85	$210.85	$210.80
Purchase #2	$190.73	10.792%	$211.3136	$211.31	$211.30	$211.30
Purchase #3	$118.42	4.845%	$124.1574	$124.16	$124.15	$124.20
Purchase #4	$210.81	5.189%	$221.7489	$221.75	$221.75	$221.70
Purchase #5	$110.32	7.479%	$118.5708	$118.57	$118.55	$118.60
Purchase #6	$40.42	6.397%	$43.0057	$43.01	$43.00	$43.00
Purchase #7	$246.55	6.396%	$262.3193	$262.32	$262.30	$262.30
7 purchase totals =	$1,103.20		$1,191.9644	$1,191.97	$1,191.90	$1,191.90