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	$164.42	13.856%	$187.202	$187.20	$187.20	$187.20
Purchase #2	$157.78	6.606%	$168.2029	$168.20	$168.20	$168.20
Purchase #3	$165.78	13.500%	$188.1603	$188.16	$188.15	$188.20
Purchase #4	$32.75	6.329%	$34.8227	$34.82	$34.80	$34.80
Purchase #5	$102.54	3.181%	$105.8018	$105.80	$105.80	$105.80
Purchase #6	$53.44	10.374%	$58.9839	$58.98	$59.00	$59.00
Purchase #7	$241.30	9.664%	$264.6192	$264.62	$264.60	$264.60
7 purchase totals =	$918.01		$1,007.7928	$1,007.78	$1,007.75	$1,007.80