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	$194.85	11.110%	$216.4978	$216.50	$216.50	$216.50
Purchase #2	$47.98	13.115%	$54.2726	$54.27	$54.25	$54.30
Purchase #3	$116.96	12.168%	$131.1917	$131.19	$131.20	$131.20
Purchase #4	$183.32	12.519%	$206.2698	$206.27	$206.25	$206.30
Purchase #5	$193.79	9.114%	$211.452	$211.45	$211.45	$211.50
Purchase #6	$149.61	11.360%	$166.6057	$166.61	$166.60	$166.60
Purchase #7	$229.51	3.493%	$237.5268	$237.53	$237.55	$237.50
7 purchase totals =	$1,116.02		$1,223.8164	$1,223.82	$1,223.80	$1,223.90