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	$115.39	13.190%	$130.6099	$130.61	$130.60	$130.60
Purchase #2	$73.59	9.731%	$80.751	$80.75	$80.75	$80.80
Purchase #3	$59.95	11.385%	$66.7753	$66.78	$66.80	$66.80
Purchase #4	$173.33	8.617%	$188.2658	$188.27	$188.25	$188.30
Purchase #5	$156.54	5.132%	$164.5736	$164.57	$164.55	$164.60
Purchase #6	$51.32	4.165%	$53.4575	$53.46	$53.45	$53.50
Purchase #7	$173.96	10.163%	$191.6396	$191.64	$191.65	$191.60
7 purchase totals =	$804.08		$876.0727	$876.08	$876.05	$876.20