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	$217.78	6.731%	$232.4388	$232.44	$232.45	$232.40
Purchase #2	$249.59	3.280%	$257.7766	$257.78	$257.80	$257.80
Purchase #3	$213.28	3.371%	$220.4697	$220.47	$220.45	$220.50
Purchase #4	$50.56	7.106%	$54.1528	$54.15	$54.15	$54.20
Purchase #5	$212.88	12.225%	$238.9046	$238.90	$238.90	$238.90
Purchase #6	$166.82	9.505%	$182.6762	$182.68	$182.70	$182.70
Purchase #7	$72.47	8.318%	$78.4981	$78.50	$78.50	$78.50
7 purchase totals =	$1,183.38		$1,264.9168	$1,264.92	$1,264.95	$1,265.00