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	$51.74	6.197%	$54.9463	$54.95	$54.95	$54.90
Purchase #2	$184.92	6.709%	$197.3263	$197.33	$197.35	$197.30
Purchase #3	$183.28	8.217%	$198.3401	$198.34	$198.35	$198.30
Purchase #4	$146.61	8.346%	$158.8461	$158.85	$158.85	$158.80
Purchase #5	$64.94	12.190%	$72.8562	$72.86	$72.85	$72.90
Purchase #6	$39.67	5.557%	$41.8745	$41.87	$41.85	$41.90
Purchase #7	$56.67	9.217%	$61.8933	$61.89	$61.90	$61.90
7 purchase totals =	$727.83		$786.0828	$786.09	$786.10	$786.00