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	$87.54	4.381%	$91.3751	$91.38	$91.40	$91.40
Purchase #2	$148.95	13.823%	$169.5394	$169.54	$169.55	$169.50
Purchase #3	$106.38	4.649%	$111.3256	$111.33	$111.35	$111.30
Purchase #4	$140.25	9.660%	$153.7982	$153.80	$153.80	$153.80
Purchase #5	$157.97	6.505%	$168.2459	$168.25	$168.25	$168.20
Purchase #6	$249.91	8.723%	$271.7096	$271.71	$271.70	$271.70
Purchase #7	$179.75	3.440%	$185.9334	$185.93	$185.95	$185.90
7 purchase totals =	$1,070.75		$1,151.9272	$1,151.94	$1,152.00	$1,151.80