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	$182.37	10.183%	$200.9407	$200.94	$200.95	$200.90
Purchase #2	$143.81	5.275%	$151.396	$151.40	$151.40	$151.40
Purchase #3	$13.74	11.185%	$15.2768	$15.28	$15.30	$15.30
Purchase #4	$112.81	9.341%	$123.3476	$123.35	$123.35	$123.30
Purchase #5	$222.97	11.325%	$248.2214	$248.22	$248.20	$248.20
Purchase #6	$103.94	8.259%	$112.5244	$112.52	$112.50	$112.50
Purchase #7	$95.69	7.186%	$102.5663	$102.57	$102.55	$102.60
7 purchase totals =	$875.33		$954.2732	$954.28	$954.25	$954.20