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	$74.39	7.705%	$80.1217	$80.12	$80.10	$80.10
Purchase #2	$66.37	9.808%	$72.8796	$72.88	$72.90	$72.90
Purchase #3	$118.28	11.367%	$131.7249	$131.72	$131.70	$131.70
Purchase #4	$134.55	6.412%	$143.1773	$143.18	$143.20	$143.20
Purchase #5	$211.38	13.275%	$239.4407	$239.44	$239.45	$239.40
Purchase #6	$167.60	11.697%	$187.2042	$187.20	$187.20	$187.20
Purchase #7	$145.80	9.476%	$159.616	$159.62	$159.60	$159.60
7 purchase totals =	$918.37		$1,014.1644	$1,014.16	$1,014.15	$1,014.10