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	$139.32	8.650%	$151.3712	$151.37	$151.35	$151.40
Purchase #2	$134.38	3.306%	$138.8226	$138.82	$138.80	$138.80
Purchase #3	$47.86	12.581%	$53.8813	$53.88	$53.90	$53.90
Purchase #4	$97.89	4.435%	$102.2314	$102.23	$102.25	$102.20
Purchase #5	$177.57	10.634%	$196.4528	$196.45	$196.45	$196.50
Purchase #6	$6.74	10.693%	$7.4607	$7.46	$7.45	$7.50
Purchase #7	$29.49	9.852%	$32.3954	$32.40	$32.40	$32.40
7 purchase totals =	$633.25		$682.6154	$682.61	$682.60	$682.70