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	$82.84	4.661%	$86.7012	$86.70	$86.70	$86.70
Purchase #2	$168.78	9.313%	$184.4985	$184.50	$184.50	$184.50
Purchase #3	$126.89	5.550%	$133.9324	$133.93	$133.95	$133.90
Purchase #4	$92.80	8.360%	$100.5581	$100.56	$100.55	$100.60
Purchase #5	$164.61	5.514%	$173.6866	$173.69	$173.70	$173.70
Purchase #6	$13.55	7.774%	$14.6034	$14.60	$14.60	$14.60
Purchase #7	$35.47	9.467%	$38.8279	$38.83	$38.85	$38.80
7 purchase totals =	$684.94		$732.8081	$732.81	$732.85	$732.80