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	$217.38	3.275%	$224.4992	$224.50	$224.50	$224.50
Purchase #2	$84.90	12.192%	$95.251	$95.25	$95.25	$95.30
Purchase #3	$74.43	11.721%	$83.1539	$83.15	$83.15	$83.20
Purchase #4	$227.89	6.116%	$241.8278	$241.83	$241.85	$241.80
Purchase #5	$250.81	9.474%	$274.5717	$274.57	$274.55	$274.60
Purchase #6	$239.75	7.499%	$257.7289	$257.73	$257.75	$257.70
Purchase #7	$105.28	6.228%	$111.8368	$111.84	$111.85	$111.80
7 purchase totals =	$1,200.44		$1,288.8693	$1,288.87	$1,288.90	$1,288.90