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	$233.43	11.694%	$260.7273	$260.73	$260.75	$260.70
Purchase #2	$28.30	13.555%	$32.1361	$32.14	$32.15	$32.10
Purchase #3	$93.29	10.659%	$103.2338	$103.23	$103.25	$103.20
Purchase #4	$233.68	6.611%	$249.1286	$249.13	$249.15	$249.10
Purchase #5	$226.88	12.626%	$255.5259	$255.53	$255.55	$255.50
Purchase #6	$39.81	9.539%	$43.6075	$43.61	$43.60	$43.60
Purchase #7	$146.78	7.371%	$157.5992	$157.60	$157.60	$157.60
7 purchase totals =	$1,002.17		$1,101.9584	$1,101.97	$1,102.05	$1,101.80