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	$101.36	10.365%	$111.866	$111.87	$111.85	$111.90
Purchase #2	$144.36	13.445%	$163.7692	$163.77	$163.75	$163.80
Purchase #3	$242.53	12.416%	$272.6425	$272.64	$272.65	$272.60
Purchase #4	$161.57	4.316%	$168.5434	$168.54	$168.55	$168.50
Purchase #5	$111.88	7.565%	$120.3437	$120.34	$120.35	$120.30
Purchase #6	$133.59	13.314%	$151.3762	$151.38	$151.40	$151.40
Purchase #7	$185.71	7.161%	$199.0087	$199.01	$199.00	$199.00
7 purchase totals =	$1,081.00		$1,187.5497	$1,187.55	$1,187.55	$1,187.50