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	$54.79	9.871%	$60.1983	$60.20	$60.20	$60.20
Purchase #2	$175.71	5.565%	$185.4883	$185.49	$185.50	$185.50
Purchase #3	$168.57	11.269%	$187.5662	$187.57	$187.55	$187.60
Purchase #4	$227.74	4.732%	$238.5167	$238.52	$238.50	$238.50
Purchase #5	$192.56	9.210%	$210.2948	$210.29	$210.30	$210.30
Purchase #6	$119.31	5.422%	$125.779	$125.78	$125.80	$125.80
Purchase #7	$148.30	10.780%	$164.2867	$164.29	$164.30	$164.30
7 purchase totals =	$1,086.98		$1,172.1300	$1,172.14	$1,172.15	$1,172.20