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	$86.89	8.590%	$94.3539	$94.35	$94.35	$94.40
Purchase #2	$249.52	3.233%	$257.587	$257.59	$257.60	$257.60
Purchase #3	$186.27	12.548%	$209.6432	$209.64	$209.65	$209.60
Purchase #4	$50.69	10.201%	$55.8609	$55.86	$55.85	$55.90
Purchase #5	$47.31	10.330%	$52.1971	$52.20	$52.20	$52.20
Purchase #6	$206.25	7.846%	$222.4324	$222.43	$222.45	$222.40
Purchase #7	$141.95	10.282%	$156.5453	$156.55	$156.55	$156.50
7 purchase totals =	$968.88		$1,048.6198	$1,048.62	$1,048.65	$1,048.60