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	$61.62	12.136%	$69.0982	$69.10	$69.10	$69.10
Purchase #2	$240.38	9.570%	$263.3844	$263.38	$263.40	$263.40
Purchase #3	$250.75	10.845%	$277.9438	$277.94	$277.95	$277.90
Purchase #4	$190.72	11.710%	$213.0533	$213.05	$213.05	$213.10
Purchase #5	$141.75	6.716%	$151.2699	$151.27	$151.25	$151.30
Purchase #6	$81.82	11.834%	$91.5026	$91.50	$91.50	$91.50
Purchase #7	$30.54	8.648%	$33.1811	$33.18	$33.20	$33.20
7 purchase totals =	$997.58		$1,099.4333	$1,099.42	$1,099.45	$1,099.50