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	$43.77	3.441%	$45.2761	$45.28	$45.30	$45.30
Purchase #2	$34.86	4.641%	$36.4779	$36.48	$36.50	$36.50
Purchase #3	$115.49	13.660%	$131.2659	$131.27	$131.25	$131.30
Purchase #4	$188.36	5.435%	$198.5974	$198.60	$198.60	$198.60
Purchase #5	$244.46	11.410%	$272.3529	$272.35	$272.35	$272.40
Purchase #6	$50.31	10.118%	$55.4004	$55.40	$55.40	$55.40
Purchase #7	$131.31	9.821%	$144.206	$144.21	$144.20	$144.20
7 purchase totals =	$808.56		$883.5766	$883.59	$883.60	$883.70