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	$169.77	5.102%	$178.4317	$178.43	$178.45	$178.40
Purchase #2	$31.51	3.450%	$32.5971	$32.60	$32.60	$32.60
Purchase #3	$36.42	11.124%	$40.4714	$40.47	$40.45	$40.50
Purchase #4	$211.96	10.516%	$234.2497	$234.25	$234.25	$234.20
Purchase #5	$224.54	5.224%	$236.27	$236.27	$236.25	$236.30
Purchase #6	$86.64	4.596%	$90.622	$90.62	$90.60	$90.60
Purchase #7	$12.60	9.273%	$13.7684	$13.77	$13.75	$13.80
7 purchase totals =	$773.44		$826.4103	$826.41	$826.35	$826.40