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	$132.87	13.667%	$151.0293	$151.03	$151.05	$151.00
Purchase #2	$75.40	9.306%	$82.4167	$82.42	$82.40	$82.40
Purchase #3	$105.64	10.114%	$116.3244	$116.32	$116.30	$116.30
Purchase #4	$84.94	5.567%	$89.6686	$89.67	$89.65	$89.70
Purchase #5	$238.80	6.744%	$254.9047	$254.90	$254.90	$254.90
Purchase #6	$145.36	12.364%	$163.3323	$163.33	$163.35	$163.30
Purchase #7	$214.85	6.283%	$228.349	$228.35	$228.35	$228.30
7 purchase totals =	$997.86		$1,086.0250	$1,086.02	$1,086.00	$1,085.90