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	$103.28	12.692%	$116.3883	$116.39	$116.40	$116.40
Purchase #2	$226.89	12.404%	$255.0334	$255.03	$255.05	$255.00
Purchase #3	$7.55	12.198%	$8.4709	$8.47	$8.45	$8.50
Purchase #4	$151.55	10.507%	$167.4734	$167.47	$167.45	$167.50
Purchase #5	$177.83	4.107%	$185.1335	$185.13	$185.15	$185.10
Purchase #6	$226.50	7.734%	$244.0175	$244.02	$244.00	$244.00
Purchase #7	$65.56	10.651%	$72.5428	$72.54	$72.55	$72.50
7 purchase totals =	$959.16		$1,049.0598	$1,049.05	$1,049.05	$1,049.00