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	$154.51	9.114%	$168.592	$168.59	$168.60	$168.60
Purchase #2	$36.46	13.853%	$41.5108	$41.51	$41.50	$41.50
Purchase #3	$41.50	6.446%	$44.1751	$44.18	$44.20	$44.20
Purchase #4	$176.44	7.687%	$190.0029	$190.00	$190.00	$190.00
Purchase #5	$204.51	5.518%	$215.7949	$215.79	$215.80	$215.80
Purchase #6	$224.75	10.360%	$248.0341	$248.03	$248.05	$248.00
Purchase #7	$61.66	9.819%	$67.7144	$67.71	$67.70	$67.70
7 purchase totals =	$899.83		$975.8242	$975.81	$975.85	$975.80