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	$156.84	7.593%	$168.7489	$168.75	$168.75	$168.70
Purchase #2	$185.92	8.191%	$201.1487	$201.15	$201.15	$201.10
Purchase #3	$232.43	10.736%	$257.3837	$257.38	$257.40	$257.40
Purchase #4	$98.45	13.662%	$111.9002	$111.90	$111.90	$111.90
Purchase #5	$72.38	13.725%	$82.3142	$82.31	$82.30	$82.30
Purchase #6	$107.26	11.367%	$119.4522	$119.45	$119.45	$119.50
Purchase #7	$62.59	6.717%	$66.7942	$66.79	$66.80	$66.80
7 purchase totals =	$915.87		$1,007.7421	$1,007.73	$1,007.75	$1,007.70