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	$156.88	6.547%	$167.1509	$167.15	$167.15	$167.20
Purchase #2	$162.52	3.705%	$168.5414	$168.54	$168.55	$168.50
Purchase #3	$63.60	13.800%	$72.3768	$72.38	$72.40	$72.40
Purchase #4	$163.33	5.622%	$172.5124	$172.51	$172.50	$172.50
Purchase #5	$88.76	8.721%	$96.5008	$96.50	$96.50	$96.50
Purchase #6	$245.72	9.583%	$269.2673	$269.27	$269.25	$269.30
Purchase #7	$40.34	6.624%	$43.0121	$43.01	$43.00	$43.00
7 purchase totals =	$921.15		$989.3617	$989.36	$989.35	$989.40