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	$36.94	9.144%	$40.3178	$40.32	$40.30	$40.30
Purchase #2	$136.81	10.749%	$151.5157	$151.52	$151.50	$151.50
Purchase #3	$162.61	4.480%	$169.8949	$169.89	$169.90	$169.90
Purchase #4	$237.47	6.352%	$252.5541	$252.55	$252.55	$252.60
Purchase #5	$184.94	12.563%	$208.174	$208.17	$208.15	$208.20
Purchase #6	$170.39	6.403%	$181.3001	$181.30	$181.30	$181.30
Purchase #7	$128.58	12.191%	$144.2552	$144.26	$144.25	$144.30
7 purchase totals =	$1,057.74		$1,148.0118	$1,148.01	$1,147.95	$1,148.10