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	$159.34	8.244%	$172.476	$172.48	$172.50	$172.50
Purchase #2	$28.90	7.317%	$31.0146	$31.01	$31.00	$31.00
Purchase #3	$247.27	5.634%	$261.2012	$261.20	$261.20	$261.20
Purchase #4	$159.64	11.675%	$178.278	$178.28	$178.30	$178.30
Purchase #5	$250.25	6.284%	$265.9757	$265.98	$266.00	$266.00
Purchase #6	$109.71	4.243%	$114.365	$114.37	$114.35	$114.40
Purchase #7	$35.94	6.757%	$38.3685	$38.37	$38.35	$38.40
7 purchase totals =	$991.05		$1,061.6790	$1,061.69	$1,061.70	$1,061.80