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	$108.41	7.412%	$116.4453	$116.45	$116.45	$116.40
Purchase #2	$61.64	10.267%	$67.9686	$67.97	$67.95	$68.00
Purchase #3	$209.37	3.326%	$216.3336	$216.33	$216.35	$216.30
Purchase #4	$156.32	10.869%	$173.3104	$173.31	$173.30	$173.30
Purchase #5	$34.90	13.582%	$39.6401	$39.64	$39.65	$39.60
Purchase #6	$115.59	13.805%	$131.5472	$131.55	$131.55	$131.50
Purchase #7	$10.87	5.409%	$11.458	$11.46	$11.45	$11.50
7 purchase totals =	$697.10		$756.7032	$756.71	$756.70	$756.60