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	$211.36	8.693%	$229.7335	$229.73	$229.75	$229.70
Purchase #2	$100.72	5.122%	$105.8789	$105.88	$105.90	$105.90
Purchase #3	$225.80	13.157%	$255.5085	$255.51	$255.50	$255.50
Purchase #4	$240.27	6.657%	$256.2648	$256.26	$256.25	$256.30
Purchase #5	$209.75	10.323%	$231.4025	$231.40	$231.40	$231.40
Purchase #6	$226.31	5.835%	$239.5152	$239.52	$239.50	$239.50
Purchase #7	$20.77	3.538%	$21.5048	$21.50	$21.50	$21.50
7 purchase totals =	$1,234.98		$1,339.8082	$1,339.80	$1,339.80	$1,339.80