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	$210.93	3.500%	$218.3126	$218.31	$218.30	$218.30
Purchase #2	$217.66	4.859%	$228.2361	$228.24	$228.25	$228.20
Purchase #3	$136.54	4.429%	$142.5874	$142.59	$142.60	$142.60
Purchase #4	$242.73	6.330%	$258.0948	$258.09	$258.10	$258.10
Purchase #5	$230.38	6.113%	$244.4631	$244.46	$244.45	$244.50
Purchase #6	$44.49	8.815%	$48.4118	$48.41	$48.40	$48.40
Purchase #7	$176.53	11.130%	$196.1778	$196.18	$196.20	$196.20
7 purchase totals =	$1,259.26		$1,336.2836	$1,336.28	$1,336.30	$1,336.30