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	$209.43	11.429%	$233.3658	$233.37	$233.35	$233.40
Purchase #2	$135.41	6.703%	$144.4865	$144.49	$144.50	$144.50
Purchase #3	$103.25	11.178%	$114.7913	$114.79	$114.80	$114.80
Purchase #4	$155.29	10.356%	$171.3718	$171.37	$171.35	$171.40
Purchase #5	$138.92	12.460%	$156.2294	$156.23	$156.25	$156.20
Purchase #6	$51.55	9.843%	$56.6241	$56.62	$56.60	$56.60
Purchase #7	$144.83	4.492%	$151.3358	$151.34	$151.35	$151.30
7 purchase totals =	$938.68		$1,028.2047	$1,028.21	$1,028.20	$1,028.20