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	$95.71	6.732%	$102.1532	$102.15	$102.15	$102.20
Purchase #2	$79.53	3.298%	$82.1529	$82.15	$82.15	$82.20
Purchase #3	$248.89	4.583%	$260.2966	$260.30	$260.30	$260.30
Purchase #4	$142.47	12.730%	$160.6064	$160.61	$160.60	$160.60
Purchase #5	$29.82	11.406%	$33.2213	$33.22	$33.20	$33.20
Purchase #6	$61.59	5.630%	$65.0575	$65.06	$65.05	$65.10
Purchase #7	$60.88	11.136%	$67.6596	$67.66	$67.65	$67.70
7 purchase totals =	$718.89		$771.1475	$771.15	$771.10	$771.30