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	$126.53	10.445%	$139.7461	$139.75	$139.75	$139.70
Purchase #2	$65.72	8.117%	$71.0545	$71.05	$71.05	$71.10
Purchase #3	$179.32	10.756%	$198.6077	$198.61	$198.60	$198.60
Purchase #4	$230.71	4.861%	$241.9248	$241.92	$241.90	$241.90
Purchase #5	$230.59	5.798%	$243.9596	$243.96	$243.95	$244.00
Purchase #6	$221.54	8.328%	$239.9899	$239.99	$240.00	$240.00
Purchase #7	$99.88	11.864%	$111.7298	$111.73	$111.75	$111.70
7 purchase totals =	$1,154.29		$1,247.0124	$1,247.01	$1,247.00	$1,247.00