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	$98.69	5.328%	$103.9482	$103.95	$103.95	$103.90
Purchase #2	$77.58	10.669%	$85.857	$85.86	$85.85	$85.90
Purchase #3	$73.58	13.643%	$83.6185	$83.62	$83.60	$83.60
Purchase #4	$208.96	11.636%	$233.2746	$233.27	$233.25	$233.30
Purchase #5	$37.78	4.748%	$39.5738	$39.57	$39.55	$39.60
Purchase #6	$6.63	6.254%	$7.0446	$7.04	$7.05	$7.00
Purchase #7	$223.47	12.591%	$251.6071	$251.61	$251.60	$251.60
7 purchase totals =	$726.69		$804.9238	$804.92	$804.85	$804.90