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	$149.59	7.537%	$160.8646	$160.86	$160.85	$160.90
Purchase #2	$127.69	9.336%	$139.6111	$139.61	$139.60	$139.60
Purchase #3	$30.32	5.255%	$31.9133	$31.91	$31.90	$31.90
Purchase #4	$8.85	13.230%	$10.0209	$10.02	$10.00	$10.00
Purchase #5	$96.26	6.384%	$102.4052	$102.41	$102.40	$102.40
Purchase #6	$44.62	5.166%	$46.9251	$46.93	$46.95	$46.90
Purchase #7	$72.92	10.345%	$80.4636	$80.46	$80.45	$80.50
7 purchase totals =	$530.25		$572.2038	$572.20	$572.15	$572.20