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	$225.50	8.350%	$244.3293	$244.33	$244.35	$244.30
Purchase #2	$185.49	10.849%	$205.6138	$205.61	$205.60	$205.60
Purchase #3	$96.45	9.173%	$105.2974	$105.30	$105.30	$105.30
Purchase #4	$36.30	9.231%	$39.6509	$39.65	$39.65	$39.70
Purchase #5	$226.56	13.384%	$256.8828	$256.88	$256.90	$256.90
Purchase #6	$109.72	6.411%	$116.7541	$116.75	$116.75	$116.80
Purchase #7	$159.77	5.473%	$168.5142	$168.51	$168.50	$168.50
7 purchase totals =	$1,039.79		$1,137.0425	$1,137.03	$1,137.05	$1,137.10