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	$52.25	7.450%	$56.1426	$56.14	$56.15	$56.10
Purchase #2	$133.68	13.721%	$152.0222	$152.02	$152.00	$152.00
Purchase #3	$90.68	8.483%	$98.3724	$98.37	$98.35	$98.40
Purchase #4	$52.78	4.505%	$55.1577	$55.16	$55.15	$55.20
Purchase #5	$244.32	4.797%	$256.04	$256.04	$256.05	$256.00
Purchase #6	$85.80	5.638%	$90.6374	$90.64	$90.65	$90.60
Purchase #7	$243.97	7.771%	$262.9289	$262.93	$262.95	$262.90
7 purchase totals =	$903.48		$971.3012	$971.30	$971.30	$971.20