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	$140.94	4.734%	$147.6121	$147.61	$147.60	$147.60
Purchase #2	$96.84	9.324%	$105.8694	$105.87	$105.85	$105.90
Purchase #3	$98.57	12.651%	$111.0401	$111.04	$111.05	$111.00
Purchase #4	$55.47	13.495%	$62.9557	$62.96	$62.95	$63.00
Purchase #5	$69.59	6.309%	$73.9804	$73.98	$74.00	$74.00
Purchase #6	$48.39	10.350%	$53.3984	$53.40	$53.40	$53.40
Purchase #7	$153.85	8.145%	$166.3811	$166.38	$166.40	$166.40
7 purchase totals =	$663.65		$721.2372	$721.24	$721.25	$721.30