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	$17.51	12.439%	$19.6881	$19.69	$19.70	$19.70
Purchase #2	$44.65	4.320%	$46.5789	$46.58	$46.60	$46.60
Purchase #3	$182.89	7.565%	$196.7256	$196.73	$196.75	$196.70
Purchase #4	$179.42	10.242%	$197.7962	$197.80	$197.80	$197.80
Purchase #5	$105.27	4.443%	$109.9471	$109.95	$109.95	$109.90
Purchase #6	$100.89	13.841%	$114.8542	$114.85	$114.85	$114.90
Purchase #7	$24.85	7.166%	$26.6308	$26.63	$26.65	$26.60
7 purchase totals =	$655.48		$712.2209	$712.23	$712.30	$712.20