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	$65.82	9.815%	$72.2802	$72.28	$72.30	$72.30
Purchase #2	$211.97	7.537%	$227.9462	$227.95	$227.95	$227.90
Purchase #3	$14.91	12.301%	$16.7441	$16.74	$16.75	$16.70
Purchase #4	$69.31	4.859%	$72.6778	$72.68	$72.70	$72.70
Purchase #5	$156.88	3.808%	$162.854	$162.85	$162.85	$162.90
Purchase #6	$244.54	8.629%	$265.6414	$265.64	$265.65	$265.60
Purchase #7	$101.47	9.500%	$111.1097	$111.11	$111.10	$111.10
7 purchase totals =	$864.90		$929.2534	$929.25	$929.30	$929.20