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	$167.32	3.649%	$173.4255	$173.43	$173.45	$173.40
Purchase #2	$31.92	6.299%	$33.9306	$33.93	$33.95	$33.90
Purchase #3	$113.63	11.297%	$126.4668	$126.47	$126.45	$126.50
Purchase #4	$246.90	13.644%	$280.587	$280.59	$280.60	$280.60
Purchase #5	$204.47	13.198%	$231.456	$231.46	$231.45	$231.50
Purchase #6	$83.74	10.296%	$92.3619	$92.36	$92.35	$92.40
Purchase #7	$190.82	7.856%	$205.8108	$205.81	$205.80	$205.80
7 purchase totals =	$1,038.80		$1,144.0386	$1,144.05	$1,144.05	$1,144.10