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	$96.65	9.283%	$105.622	$105.62	$105.60	$105.60
Purchase #2	$182.51	10.254%	$201.2246	$201.22	$201.20	$201.20
Purchase #3	$92.90	11.330%	$103.4256	$103.43	$103.45	$103.40
Purchase #4	$218.71	10.431%	$241.5236	$241.52	$241.50	$241.50
Purchase #5	$68.50	5.701%	$72.4052	$72.41	$72.40	$72.40
Purchase #6	$202.75	13.325%	$229.7664	$229.77	$229.75	$229.80
Purchase #7	$78.86	12.816%	$88.9667	$88.97	$88.95	$89.00
7 purchase totals =	$940.88		$1,042.9341	$1,042.94	$1,042.85	$1,042.90