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	$237.68	10.634%	$262.9549	$262.95	$262.95	$263.00
Purchase #2	$136.28	8.151%	$147.3882	$147.39	$147.40	$147.40
Purchase #3	$149.71	7.491%	$160.9248	$160.92	$160.90	$160.90
Purchase #4	$204.60	9.281%	$223.5889	$223.59	$223.60	$223.60
Purchase #5	$13.85	10.609%	$15.3193	$15.32	$15.30	$15.30
Purchase #6	$183.98	6.836%	$196.5569	$196.56	$196.55	$196.60
Purchase #7	$222.90	5.828%	$235.8906	$235.89	$235.90	$235.90
7 purchase totals =	$1,149.00		$1,242.6236	$1,242.62	$1,242.60	$1,242.70