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	$90.46	6.224%	$96.0902	$96.09	$96.10	$96.10
Purchase #2	$140.82	6.588%	$150.0972	$150.10	$150.10	$150.10
Purchase #3	$90.84	7.344%	$97.5113	$97.51	$97.50	$97.50
Purchase #4	$16.63	13.132%	$18.8139	$18.81	$18.80	$18.80
Purchase #5	$94.42	6.150%	$100.2268	$100.23	$100.25	$100.20
Purchase #6	$197.78	9.215%	$216.0054	$216.01	$216.00	$216.00
Purchase #7	$24.95	10.373%	$27.5381	$27.54	$27.55	$27.50
7 purchase totals =	$655.90		$706.2829	$706.29	$706.30	$706.20