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	$152.80	9.615%	$167.4917	$167.49	$167.50	$167.50
Purchase #2	$17.65	5.665%	$18.6499	$18.65	$18.65	$18.60
Purchase #3	$54.40	8.262%	$58.8945	$58.89	$58.90	$58.90
Purchase #4	$98.43	10.265%	$108.5338	$108.53	$108.55	$108.50
Purchase #5	$194.50	10.705%	$215.3212	$215.32	$215.30	$215.30
Purchase #6	$62.98	5.443%	$66.408	$66.41	$66.40	$66.40
Purchase #7	$54.91	9.562%	$60.1605	$60.16	$60.15	$60.20
7 purchase totals =	$635.67		$695.4596	$695.45	$695.45	$695.40