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	$204.97	10.552%	$226.5984	$226.60	$226.60	$226.60
Purchase #2	$173.83	7.634%	$187.1002	$187.10	$187.10	$187.10
Purchase #3	$12.82	4.620%	$13.4123	$13.41	$13.40	$13.40
Purchase #4	$210.33	3.755%	$218.2279	$218.23	$218.25	$218.20
Purchase #5	$90.83	5.507%	$95.832	$95.83	$95.85	$95.80
Purchase #6	$94.33	5.390%	$99.4144	$99.41	$99.40	$99.40
Purchase #7	$167.62	4.605%	$175.3389	$175.34	$175.35	$175.30
7 purchase totals =	$954.73		$1,015.9241	$1,015.92	$1,015.95	$1,015.80