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	$39.70	11.460%	$44.2496	$44.25	$44.25	$44.20
Purchase #2	$242.72	4.550%	$253.7638	$253.76	$253.75	$253.80
Purchase #3	$196.77	7.754%	$212.0275	$212.03	$212.05	$212.00
Purchase #4	$113.50	11.690%	$126.7682	$126.77	$126.75	$126.80
Purchase #5	$81.92	10.383%	$90.4258	$90.43	$90.45	$90.40
Purchase #6	$172.93	8.555%	$187.7242	$187.72	$187.70	$187.70
Purchase #7	$138.65	8.630%	$150.6155	$150.62	$150.60	$150.60
7 purchase totals =	$986.19		$1,065.5746	$1,065.58	$1,065.55	$1,065.50