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	$105.39	12.390%	$118.4478	$118.45	$118.45	$118.40
Purchase #2	$41.33	8.655%	$44.9071	$44.91	$44.90	$44.90
Purchase #3	$72.52	13.864%	$82.5742	$82.57	$82.55	$82.60
Purchase #4	$167.74	7.102%	$179.6529	$179.65	$179.65	$179.70
Purchase #5	$176.29	5.136%	$185.3443	$185.34	$185.35	$185.30
Purchase #6	$166.35	8.807%	$181.0004	$181.00	$181.00	$181.00
Purchase #7	$236.69	8.510%	$256.8323	$256.83	$256.85	$256.80
7 purchase totals =	$966.31		$1,048.7590	$1,048.75	$1,048.75	$1,048.70