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	$173.34	4.344%	$180.8699	$180.87	$180.85	$180.90
Purchase #2	$44.69	9.416%	$48.898	$48.90	$48.90	$48.90
Purchase #3	$144.95	10.114%	$159.6102	$159.61	$159.60	$159.60
Purchase #4	$142.71	13.671%	$162.2199	$162.22	$162.20	$162.20
Purchase #5	$82.34	4.206%	$85.8032	$85.80	$85.80	$85.80
Purchase #6	$216.52	7.808%	$233.4259	$233.43	$233.45	$233.40
Purchase #7	$250.43	6.544%	$266.8181	$266.82	$266.80	$266.80
7 purchase totals =	$1,054.98		$1,137.6452	$1,137.65	$1,137.60	$1,137.60