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	$238.97	11.138%	$265.5865	$265.59	$265.60	$265.60
Purchase #2	$225.30	12.372%	$253.1741	$253.17	$253.15	$253.20
Purchase #3	$64.33	4.153%	$67.0016	$67.00	$67.00	$67.00
Purchase #4	$101.27	9.710%	$111.1033	$111.10	$111.10	$111.10
Purchase #5	$150.95	3.650%	$156.4597	$156.46	$156.45	$156.50
Purchase #6	$160.79	7.418%	$172.7174	$172.72	$172.70	$172.70
Purchase #7	$98.88	5.124%	$103.9466	$103.95	$103.95	$103.90
7 purchase totals =	$1,040.49		$1,129.9892	$1,129.99	$1,129.95	$1,130.00