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	$52.56	7.759%	$56.6381	$56.64	$56.65	$56.60
Purchase #2	$74.91	4.739%	$78.46	$78.46	$78.45	$78.50
Purchase #3	$219.31	10.531%	$242.4055	$242.41	$242.40	$242.40
Purchase #4	$60.88	10.785%	$67.4459	$67.45	$67.45	$67.40
Purchase #5	$168.68	3.265%	$174.1874	$174.19	$174.20	$174.20
Purchase #6	$118.95	12.282%	$133.5594	$133.56	$133.55	$133.60
Purchase #7	$24.42	11.553%	$27.2412	$27.24	$27.25	$27.20
7 purchase totals =	$719.71		$779.9375	$779.95	$779.95	$779.90