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	$64.31	8.853%	$70.0034	$70.00	$70.00	$70.00
Purchase #2	$157.62	4.140%	$164.1455	$164.15	$164.15	$164.10
Purchase #3	$176.43	11.587%	$196.8729	$196.87	$196.85	$196.90
Purchase #4	$156.97	3.297%	$162.1453	$162.15	$162.15	$162.10
Purchase #5	$166.47	13.161%	$188.3791	$188.38	$188.40	$188.40
Purchase #6	$66.31	7.667%	$71.394	$71.39	$71.40	$71.40
Purchase #7	$90.66	3.803%	$94.1078	$94.11	$94.10	$94.10
7 purchase totals =	$878.77		$947.0480	$947.05	$947.05	$947.00