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	$97.26	11.715%	$108.654	$108.65	$108.65	$108.70
Purchase #2	$107.35	9.586%	$117.6406	$117.64	$117.65	$117.60
Purchase #3	$14.50	8.797%	$15.7756	$15.78	$15.80	$15.80
Purchase #4	$111.73	10.790%	$123.7857	$123.79	$123.80	$123.80
Purchase #5	$100.95	8.203%	$109.2309	$109.23	$109.25	$109.20
Purchase #6	$170.61	8.619%	$185.3149	$185.31	$185.30	$185.30
Purchase #7	$55.93	6.354%	$59.4838	$59.48	$59.50	$59.50
7 purchase totals =	$658.33		$719.8855	$719.88	$719.95	$719.90