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	$39.71	9.291%	$43.3995	$43.40	$43.40	$43.40
Purchase #2	$145.28	4.757%	$152.191	$152.19	$152.20	$152.20
Purchase #3	$125.50	13.863%	$142.8981	$142.90	$142.90	$142.90
Purchase #4	$129.48	5.576%	$136.6998	$136.70	$136.70	$136.70
Purchase #5	$119.92	4.559%	$125.3872	$125.39	$125.40	$125.40
Purchase #6	$134.73	4.772%	$141.1593	$141.16	$141.15	$141.20
Purchase #7	$153.42	12.511%	$172.6144	$172.61	$172.60	$172.60
7 purchase totals =	$848.04		$914.3493	$914.35	$914.35	$914.40