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	$147.36	4.159%	$153.4887	$153.49	$153.50	$153.50
Purchase #2	$139.34	4.418%	$145.496	$145.50	$145.50	$145.50
Purchase #3	$48.36	12.693%	$54.4983	$54.50	$54.50	$54.50
Purchase #4	$134.72	11.459%	$150.1576	$150.16	$150.15	$150.20
Purchase #5	$182.86	11.799%	$204.4357	$204.44	$204.45	$204.40
Purchase #6	$243.36	11.497%	$271.3391	$271.34	$271.35	$271.30
Purchase #7	$117.50	7.395%	$126.1891	$126.19	$126.20	$126.20
7 purchase totals =	$1,013.50		$1,105.6045	$1,105.62	$1,105.65	$1,105.60