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	$245.77	10.783%	$272.2714	$272.27	$272.25	$272.30
Purchase #2	$103.52	5.662%	$109.3813	$109.38	$109.40	$109.40
Purchase #3	$215.89	3.457%	$223.3533	$223.35	$223.35	$223.40
Purchase #4	$109.35	8.280%	$118.4042	$118.40	$118.40	$118.40
Purchase #5	$177.72	8.871%	$193.4855	$193.49	$193.50	$193.50
Purchase #6	$152.33	13.723%	$173.2342	$173.23	$173.25	$173.20
Purchase #7	$120.52	10.640%	$133.3433	$133.34	$133.35	$133.30
7 purchase totals =	$1,125.10		$1,223.4732	$1,223.46	$1,223.50	$1,223.50