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	$233.74	4.291%	$243.7698	$243.77	$243.75	$243.80
Purchase #2	$54.49	4.818%	$57.1153	$57.12	$57.10	$57.10
Purchase #3	$73.78	10.277%	$81.3624	$81.36	$81.35	$81.40
Purchase #4	$177.42	11.693%	$198.1657	$198.17	$198.15	$198.20
Purchase #5	$227.48	10.276%	$250.8558	$250.86	$250.85	$250.90
Purchase #6	$158.60	8.646%	$172.3126	$172.31	$172.30	$172.30
Purchase #7	$29.51	11.698%	$32.9621	$32.96	$32.95	$33.00
7 purchase totals =	$955.02		$1,036.5437	$1,036.55	$1,036.45	$1,036.70