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	$161.59	9.598%	$177.0994	$177.10	$177.10	$177.10
Purchase #2	$154.82	6.647%	$165.1109	$165.11	$165.10	$165.10
Purchase #3	$229.59	13.169%	$259.8247	$259.82	$259.80	$259.80
Purchase #4	$34.39	12.359%	$38.6403	$38.64	$38.65	$38.60
Purchase #5	$186.30	10.495%	$205.8522	$205.85	$205.85	$205.90
Purchase #6	$14.28	9.711%	$15.6667	$15.67	$15.65	$15.70
Purchase #7	$222.93	11.737%	$249.0953	$249.10	$249.10	$249.10
7 purchase totals =	$1,003.90		$1,111.2895	$1,111.29	$1,111.25	$1,111.30