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	$239.72	7.147%	$256.8528	$256.85	$256.85	$256.90
Purchase #2	$168.90	13.364%	$191.4718	$191.47	$191.45	$191.50
Purchase #3	$248.65	6.288%	$264.2851	$264.29	$264.30	$264.30
Purchase #4	$53.65	12.120%	$60.1524	$60.15	$60.15	$60.20
Purchase #5	$16.72	6.855%	$17.8662	$17.87	$17.85	$17.90
Purchase #6	$154.34	5.172%	$162.3225	$162.32	$162.30	$162.30
Purchase #7	$54.34	3.183%	$56.0696	$56.07	$56.05	$56.10
7 purchase totals =	$936.32		$1,009.0204	$1,009.02	$1,008.95	$1,009.20