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	$39.48	11.825%	$44.1485	$44.15	$44.15	$44.10
Purchase #2	$192.50	13.595%	$218.6704	$218.67	$218.65	$218.70
Purchase #3	$56.45	7.295%	$60.568	$60.57	$60.55	$60.60
Purchase #4	$186.42	10.686%	$206.3408	$206.34	$206.35	$206.30
Purchase #5	$170.92	11.439%	$190.4715	$190.47	$190.45	$190.50
Purchase #6	$148.88	4.164%	$155.0794	$155.08	$155.10	$155.10
Purchase #7	$173.52	7.316%	$186.2147	$186.21	$186.20	$186.20
7 purchase totals =	$968.17		$1,061.4933	$1,061.49	$1,061.45	$1,061.50