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	$116.26	6.307%	$123.5925	$123.59	$123.60	$123.60
Purchase #2	$240.59	7.692%	$259.0962	$259.10	$259.10	$259.10
Purchase #3	$165.70	3.699%	$171.8292	$171.83	$171.85	$171.80
Purchase #4	$160.66	13.194%	$181.8575	$181.86	$181.85	$181.90
Purchase #5	$222.53	7.109%	$238.3497	$238.35	$238.35	$238.30
Purchase #6	$38.28	11.675%	$42.7492	$42.75	$42.75	$42.70
Purchase #7	$12.37	12.476%	$13.9133	$13.91	$13.90	$13.90
7 purchase totals =	$956.39		$1,031.3876	$1,031.39	$1,031.40	$1,031.30