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	$143.51	11.114%	$159.4597	$159.46	$159.45	$159.50
Purchase #2	$127.56	13.797%	$145.1595	$145.16	$145.15	$145.20
Purchase #3	$140.25	12.715%	$158.0828	$158.08	$158.10	$158.10
Purchase #4	$52.55	4.421%	$54.8732	$54.87	$54.85	$54.90
Purchase #5	$190.71	7.445%	$204.9084	$204.91	$204.90	$204.90
Purchase #6	$186.28	9.578%	$204.1219	$204.12	$204.10	$204.10
Purchase #7	$130.50	10.783%	$144.5718	$144.57	$144.55	$144.60
7 purchase totals =	$971.36		$1,071.1773	$1,071.17	$1,071.10	$1,071.30