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	$82.94	6.873%	$88.6405	$88.64	$88.65	$88.60
Purchase #2	$87.49	12.597%	$98.5111	$98.51	$98.50	$98.50
Purchase #3	$160.78	11.275%	$178.9079	$178.91	$178.90	$178.90
Purchase #4	$61.80	5.273%	$65.0587	$65.06	$65.05	$65.10
Purchase #5	$97.66	8.421%	$105.8839	$105.88	$105.90	$105.90
Purchase #6	$134.62	12.838%	$151.9025	$151.90	$151.90	$151.90
Purchase #7	$172.31	12.313%	$193.5265	$193.53	$193.55	$193.50
7 purchase totals =	$797.60		$882.4311	$882.43	$882.45	$882.40