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	$73.56	6.169%	$78.0979	$78.10	$78.10	$78.10
Purchase #2	$19.69	9.660%	$21.5921	$21.59	$21.60	$21.60
Purchase #3	$111.62	13.474%	$126.6597	$126.66	$126.65	$126.70
Purchase #4	$29.66	11.828%	$33.1682	$33.17	$33.15	$33.20
Purchase #5	$199.26	5.797%	$210.8111	$210.81	$210.80	$210.80
Purchase #6	$98.77	13.613%	$112.2156	$112.22	$112.20	$112.20
Purchase #7	$229.31	6.535%	$244.2954	$244.30	$244.30	$244.30
7 purchase totals =	$761.87		$826.8400	$826.85	$826.80	$826.90