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	$45.43	5.415%	$47.89	$47.89	$47.90	$47.90
Purchase #2	$247.59	6.632%	$264.0102	$264.01	$264.00	$264.00
Purchase #3	$112.90	6.549%	$120.2938	$120.29	$120.30	$120.30
Purchase #4	$62.99	4.605%	$65.8907	$65.89	$65.90	$65.90
Purchase #5	$216.92	9.538%	$237.6098	$237.61	$237.60	$237.60
Purchase #6	$241.47	5.815%	$255.5115	$255.51	$255.50	$255.50
Purchase #7	$49.41	8.757%	$53.7368	$53.74	$53.75	$53.70
7 purchase totals =	$976.71		$1,044.9428	$1,044.94	$1,044.95	$1,044.90