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	$191.72	9.846%	$210.5968	$210.60	$210.60	$210.60
Purchase #2	$29.68	7.656%	$31.9523	$31.95	$31.95	$32.00
Purchase #3	$87.30	12.665%	$98.3565	$98.36	$98.35	$98.40
Purchase #4	$37.31	7.467%	$40.0959	$40.10	$40.10	$40.10
Purchase #5	$13.67	6.601%	$14.5724	$14.57	$14.55	$14.60
Purchase #6	$56.56	5.197%	$59.4994	$59.50	$59.50	$59.50
Purchase #7	$156.26	5.160%	$164.323	$164.32	$164.30	$164.30
7 purchase totals =	$572.50		$619.3963	$619.40	$619.35	$619.50