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	$134.48	13.197%	$152.2273	$152.23	$152.25	$152.20
Purchase #2	$169.96	11.283%	$189.1366	$189.14	$189.15	$189.10
Purchase #3	$183.26	9.602%	$200.8566	$200.86	$200.85	$200.90
Purchase #4	$56.80	4.858%	$59.5593	$59.56	$59.55	$59.60
Purchase #5	$114.31	7.626%	$123.0273	$123.03	$123.05	$123.00
Purchase #6	$169.79	8.587%	$184.3699	$184.37	$184.35	$184.40
Purchase #7	$188.84	10.250%	$208.1961	$208.20	$208.20	$208.20
7 purchase totals =	$1,017.44		$1,117.3731	$1,117.39	$1,117.40	$1,117.40