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	$239.71	10.742%	$265.4596	$265.46	$265.45	$265.50
Purchase #2	$136.28	9.234%	$148.8641	$148.86	$148.85	$148.90
Purchase #3	$145.76	5.435%	$153.6821	$153.68	$153.70	$153.70
Purchase #4	$59.83	10.209%	$65.938	$65.94	$65.95	$65.90
Purchase #5	$19.72	13.795%	$22.4404	$22.44	$22.45	$22.40
Purchase #6	$125.42	12.744%	$141.4035	$141.40	$141.40	$141.40
Purchase #7	$225.50	13.148%	$255.1487	$255.15	$255.15	$255.10
7 purchase totals =	$952.22		$1,052.9364	$1,052.93	$1,052.95	$1,052.90