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	$149.75	7.752%	$161.3586	$161.36	$161.35	$161.40
Purchase #2	$244.47	4.692%	$255.9405	$255.94	$255.95	$255.90
Purchase #3	$40.46	7.462%	$43.4791	$43.48	$43.50	$43.50
Purchase #4	$224.28	6.343%	$238.5061	$238.51	$238.50	$238.50
Purchase #5	$175.95	6.841%	$187.9867	$187.99	$188.00	$188.00
Purchase #6	$52.35	7.796%	$56.4312	$56.43	$56.45	$56.40
Purchase #7	$232.37	13.872%	$264.6044	$264.60	$264.60	$264.60
7 purchase totals =	$1,119.63		$1,208.3066	$1,208.31	$1,208.35	$1,208.30