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	$62.86	7.345%	$67.4771	$67.48	$67.50	$67.50
Purchase #2	$163.53	9.545%	$179.1389	$179.14	$179.15	$179.10
Purchase #3	$207.37	4.671%	$217.0563	$217.06	$217.05	$217.10
Purchase #4	$62.75	3.360%	$64.8584	$64.86	$64.85	$64.90
Purchase #5	$129.94	11.288%	$144.6076	$144.61	$144.60	$144.60
Purchase #6	$135.59	4.857%	$142.1756	$142.18	$142.20	$142.20
Purchase #7	$190.30	5.583%	$200.9244	$200.92	$200.90	$200.90
7 purchase totals =	$952.34		$1,016.2383	$1,016.25	$1,016.25	$1,016.30