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	$61.38	9.712%	$67.3412	$67.34	$67.35	$67.30
Purchase #2	$190.51	4.777%	$199.6107	$199.61	$199.60	$199.60
Purchase #3	$104.56	11.201%	$116.2718	$116.27	$116.25	$116.30
Purchase #4	$107.69	8.482%	$116.8243	$116.82	$116.80	$116.80
Purchase #5	$118.68	4.567%	$124.1001	$124.10	$124.10	$124.10
Purchase #6	$46.72	7.833%	$50.3796	$50.38	$50.40	$50.40
Purchase #7	$6.51	5.241%	$6.8512	$6.85	$6.85	$6.90
7 purchase totals =	$636.05		$681.3789	$681.37	$681.35	$681.40