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	$224.68	4.497%	$234.7839	$234.78	$234.80	$234.80
Purchase #2	$137.28	4.274%	$143.1473	$143.15	$143.15	$143.10
Purchase #3	$177.46	7.210%	$190.2549	$190.25	$190.25	$190.30
Purchase #4	$125.89	13.132%	$142.4219	$142.42	$142.40	$142.40
Purchase #5	$36.60	3.698%	$37.9535	$37.95	$37.95	$38.00
Purchase #6	$174.64	10.402%	$192.8061	$192.81	$192.80	$192.80
Purchase #7	$205.69	3.614%	$213.1236	$213.12	$213.10	$213.10
7 purchase totals =	$1,082.24		$1,154.4912	$1,154.48	$1,154.45	$1,154.50