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	$169.51	13.400%	$192.2243	$192.22	$192.20	$192.20
Purchase #2	$125.96	12.121%	$141.2276	$141.23	$141.25	$141.20
Purchase #3	$175.72	5.745%	$185.8151	$185.82	$185.80	$185.80
Purchase #4	$248.39	4.428%	$259.3887	$259.39	$259.40	$259.40
Purchase #5	$132.46	9.592%	$145.1656	$145.17	$145.15	$145.20
Purchase #6	$117.41	9.367%	$128.4078	$128.41	$128.40	$128.40
Purchase #7	$19.95	6.754%	$21.2974	$21.30	$21.30	$21.30
7 purchase totals =	$989.40		$1,073.5265	$1,073.54	$1,073.50	$1,073.50