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	$75.44	9.810%	$82.8407	$82.84	$82.85	$82.80
Purchase #2	$44.89	4.313%	$46.8261	$46.83	$46.85	$46.80
Purchase #3	$55.29	9.464%	$60.5226	$60.52	$60.50	$60.50
Purchase #4	$106.60	3.462%	$110.2905	$110.29	$110.30	$110.30
Purchase #5	$57.85	8.215%	$62.6024	$62.60	$62.60	$62.60
Purchase #6	$157.83	7.222%	$169.2285	$169.23	$169.25	$169.20
Purchase #7	$169.46	12.280%	$190.2697	$190.27	$190.25	$190.30
7 purchase totals =	$667.36		$722.5805	$722.58	$722.60	$722.50