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	$225.49	5.470%	$237.8243	$237.82	$237.80	$237.80
Purchase #2	$72.39	13.308%	$82.0237	$82.02	$82.00	$82.00
Purchase #3	$160.33	4.218%	$167.0927	$167.09	$167.10	$167.10
Purchase #4	$127.35	13.583%	$144.648	$144.65	$144.65	$144.60
Purchase #5	$249.56	5.492%	$263.2658	$263.27	$263.25	$263.30
Purchase #6	$103.70	4.535%	$108.4028	$108.40	$108.40	$108.40
Purchase #7	$138.52	4.330%	$144.5179	$144.52	$144.50	$144.50
7 purchase totals =	$1,077.34		$1,147.7752	$1,147.77	$1,147.70	$1,147.70