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	$55.56	13.134%	$62.8573	$62.86	$62.85	$62.90
Purchase #2	$195.59	11.237%	$217.5684	$217.57	$217.55	$217.60
Purchase #3	$160.45	4.222%	$167.2242	$167.22	$167.20	$167.20
Purchase #4	$149.86	7.640%	$161.3093	$161.31	$161.30	$161.30
Purchase #5	$59.47	4.193%	$61.9636	$61.96	$61.95	$62.00
Purchase #6	$175.69	6.500%	$187.1099	$187.11	$187.10	$187.10
Purchase #7	$98.77	13.851%	$112.4506	$112.45	$112.45	$112.50
7 purchase totals =	$895.39		$970.4833	$970.48	$970.40	$970.60