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	$36.62	6.354%	$38.9468	$38.95	$38.95	$38.90
Purchase #2	$85.82	7.812%	$92.5243	$92.52	$92.50	$92.50
Purchase #3	$218.79	6.773%	$233.6086	$233.61	$233.60	$233.60
Purchase #4	$122.83	7.857%	$132.4808	$132.48	$132.50	$132.50
Purchase #5	$242.98	5.320%	$255.9065	$255.91	$255.90	$255.90
Purchase #6	$209.40	6.222%	$222.4289	$222.43	$222.45	$222.40
Purchase #7	$134.57	10.252%	$148.3661	$148.37	$148.35	$148.40
7 purchase totals =	$1,051.01		$1,124.2620	$1,124.27	$1,124.25	$1,124.20