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	$100.41	11.204%	$111.6599	$111.66	$111.65	$111.70
Purchase #2	$64.98	7.369%	$69.7684	$69.77	$69.75	$69.80
Purchase #3	$112.38	13.766%	$127.8502	$127.85	$127.85	$127.90
Purchase #4	$112.84	9.614%	$123.6884	$123.69	$123.70	$123.70
Purchase #5	$108.96	6.570%	$116.1187	$116.12	$116.10	$116.10
Purchase #6	$228.28	12.627%	$257.1049	$257.10	$257.10	$257.10
Purchase #7	$159.30	13.523%	$180.8421	$180.84	$180.85	$180.80
7 purchase totals =	$887.15		$987.0326	$987.03	$987.00	$987.10