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	$119.91	5.401%	$126.3863	$126.39	$126.40	$126.40
Purchase #2	$64.76	3.278%	$66.8828	$66.88	$66.90	$66.90
Purchase #3	$194.46	13.563%	$220.8346	$220.83	$220.85	$220.80
Purchase #4	$98.46	13.180%	$111.437	$111.44	$111.45	$111.40
Purchase #5	$216.93	11.289%	$241.4192	$241.42	$241.40	$241.40
Purchase #6	$226.35	6.162%	$240.2977	$240.30	$240.30	$240.30
Purchase #7	$100.54	4.319%	$104.8823	$104.88	$104.90	$104.90
7 purchase totals =	$1,021.41		$1,112.1399	$1,112.14	$1,112.20	$1,112.10