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	$250.74	9.533%	$274.643	$274.64	$274.65	$274.60
Purchase #2	$123.30	6.551%	$131.3774	$131.38	$131.40	$131.40
Purchase #3	$173.34	11.413%	$193.1233	$193.12	$193.10	$193.10
Purchase #4	$222.73	6.734%	$237.7286	$237.73	$237.75	$237.70
Purchase #5	$102.94	8.238%	$111.4202	$111.42	$111.40	$111.40
Purchase #6	$33.83	9.509%	$37.0469	$37.05	$37.05	$37.00
Purchase #7	$240.74	12.466%	$270.7506	$270.75	$270.75	$270.80
7 purchase totals =	$1,147.62		$1,256.0900	$1,256.09	$1,256.10	$1,256.00