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	$59.75	12.243%	$67.0652	$67.07	$67.05	$67.10
Purchase #2	$73.42	7.506%	$78.9309	$78.93	$78.95	$78.90
Purchase #3	$116.52	8.384%	$126.289	$126.29	$126.30	$126.30
Purchase #4	$173.42	11.274%	$192.9714	$192.97	$192.95	$193.00
Purchase #5	$104.47	10.492%	$115.431	$115.43	$115.45	$115.40
Purchase #6	$17.66	5.185%	$18.5757	$18.58	$18.60	$18.60
Purchase #7	$157.91	6.148%	$167.6183	$167.62	$167.60	$167.60
7 purchase totals =	$703.15		$766.8815	$766.89	$766.90	$766.90