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	$168.83	11.189%	$187.7204	$187.72	$187.70	$187.70
Purchase #2	$65.73	7.505%	$70.663	$70.66	$70.65	$70.70
Purchase #3	$16.90	13.279%	$19.1442	$19.14	$19.15	$19.10
Purchase #4	$230.73	4.458%	$241.0159	$241.02	$241.00	$241.00
Purchase #5	$148.91	11.103%	$165.4435	$165.44	$165.45	$165.40
Purchase #6	$119.85	9.571%	$131.3208	$131.32	$131.30	$131.30
Purchase #7	$227.68	6.864%	$243.308	$243.31	$243.30	$243.30
7 purchase totals =	$978.63		$1,058.6158	$1,058.61	$1,058.55	$1,058.50