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	$124.35	9.308%	$135.9245	$135.92	$135.90	$135.90
Purchase #2	$166.60	12.466%	$187.3684	$187.37	$187.35	$187.40
Purchase #3	$142.99	4.109%	$148.8655	$148.87	$148.85	$148.90
Purchase #4	$189.94	11.482%	$211.7489	$211.75	$211.75	$211.70
Purchase #5	$114.61	4.585%	$119.8649	$119.86	$119.85	$119.90
Purchase #6	$227.33	6.850%	$242.9021	$242.90	$242.90	$242.90
Purchase #7	$27.77	3.824%	$28.8319	$28.83	$28.85	$28.80
7 purchase totals =	$993.59		$1,075.5062	$1,075.50	$1,075.45	$1,075.50