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	$107.25	4.488%	$112.0634	$112.06	$112.05	$112.10
Purchase #2	$233.82	10.210%	$257.693	$257.69	$257.70	$257.70
Purchase #3	$175.56	11.655%	$196.0215	$196.02	$196.00	$196.00
Purchase #4	$92.75	8.133%	$100.2934	$100.29	$100.30	$100.30
Purchase #5	$160.67	6.323%	$170.8292	$170.83	$170.85	$170.80
Purchase #6	$108.71	3.780%	$112.8192	$112.82	$112.80	$112.80
Purchase #7	$246.28	12.125%	$276.1415	$276.14	$276.15	$276.10
7 purchase totals =	$1,125.04		$1,225.8612	$1,225.85	$1,225.85	$1,225.80