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	$59.82	12.265%	$67.1569	$67.16	$67.15	$67.20
Purchase #2	$36.32	5.449%	$38.2991	$38.30	$38.30	$38.30
Purchase #3	$189.47	5.644%	$200.1637	$200.16	$200.15	$200.20
Purchase #4	$90.29	12.874%	$101.9139	$101.91	$101.90	$101.90
Purchase #5	$244.84	4.396%	$255.6032	$255.60	$255.60	$255.60
Purchase #6	$218.64	5.558%	$230.792	$230.79	$230.80	$230.80
Purchase #7	$248.54	6.805%	$265.4531	$265.45	$265.45	$265.50
7 purchase totals =	$1,087.92		$1,159.3819	$1,159.37	$1,159.35	$1,159.50