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	$100.52	7.257%	$107.8147	$107.81	$107.80	$107.80
Purchase #2	$94.56	5.717%	$99.966	$99.97	$99.95	$100.00
Purchase #3	$246.53	13.590%	$280.0334	$280.03	$280.05	$280.00
Purchase #4	$95.84	4.500%	$100.1528	$100.15	$100.15	$100.20
Purchase #5	$142.51	9.504%	$156.0542	$156.05	$156.05	$156.10
Purchase #6	$184.70	6.431%	$196.5781	$196.58	$196.60	$196.60
Purchase #7	$173.37	6.372%	$184.4171	$184.42	$184.40	$184.40
7 purchase totals =	$1,038.03		$1,125.0163	$1,125.01	$1,125.00	$1,125.10