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	$57.38	11.752%	$64.1233	$64.12	$64.10	$64.10
Purchase #2	$211.80	12.525%	$238.328	$238.33	$238.35	$238.30
Purchase #3	$105.27	5.838%	$111.4157	$111.42	$111.40	$111.40
Purchase #4	$241.90	8.114%	$261.5278	$261.53	$261.55	$261.50
Purchase #5	$225.98	13.501%	$256.4896	$256.49	$256.50	$256.50
Purchase #6	$32.47	6.496%	$34.5793	$34.58	$34.60	$34.60
Purchase #7	$186.94	11.453%	$208.3502	$208.35	$208.35	$208.40
7 purchase totals =	$1,061.74		$1,174.8139	$1,174.82	$1,174.85	$1,174.80