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	$141.78	8.484%	$153.8086	$153.81	$153.80	$153.80
Purchase #2	$248.74	9.515%	$272.4076	$272.41	$272.40	$272.40
Purchase #3	$169.25	9.234%	$184.8785	$184.88	$184.90	$184.90
Purchase #4	$143.50	11.702%	$160.2924	$160.29	$160.30	$160.30
Purchase #5	$38.51	9.668%	$42.2331	$42.23	$42.25	$42.20
Purchase #6	$160.32	4.450%	$167.4542	$167.45	$167.45	$167.50
Purchase #7	$114.35	10.868%	$126.7776	$126.78	$126.80	$126.80
7 purchase totals =	$1,016.45		$1,107.8520	$1,107.85	$1,107.90	$1,107.90