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	$77.67	4.375%	$81.0681	$81.07	$81.05	$81.10
Purchase #2	$175.26	8.457%	$190.0817	$190.08	$190.10	$190.10
Purchase #3	$233.38	6.429%	$248.384	$248.38	$248.40	$248.40
Purchase #4	$97.83	7.576%	$105.2416	$105.24	$105.25	$105.20
Purchase #5	$147.66	11.254%	$164.2777	$164.28	$164.30	$164.30
Purchase #6	$62.72	8.183%	$67.8524	$67.85	$67.85	$67.90
Purchase #7	$90.85	8.161%	$98.2643	$98.26	$98.25	$98.30
7 purchase totals =	$885.37		$955.1698	$955.16	$955.20	$955.30