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	$209.49	4.478%	$218.871	$218.87	$218.85	$218.90
Purchase #2	$153.59	11.555%	$171.3373	$171.34	$171.35	$171.30
Purchase #3	$116.67	10.523%	$128.9472	$128.95	$128.95	$128.90
Purchase #4	$27.30	5.603%	$28.8296	$28.83	$28.85	$28.80
Purchase #5	$127.39	4.159%	$132.6882	$132.69	$132.70	$132.70
Purchase #6	$113.36	3.443%	$117.263	$117.26	$117.25	$117.30
Purchase #7	$11.91	5.128%	$12.5207	$12.52	$12.50	$12.50
7 purchase totals =	$759.71		$810.4570	$810.46	$810.45	$810.40