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	$41.47	8.863%	$45.1455	$45.15	$45.15	$45.10
Purchase #2	$92.86	6.757%	$99.1346	$99.13	$99.15	$99.10
Purchase #3	$172.45	6.228%	$183.1902	$183.19	$183.20	$183.20
Purchase #4	$222.30	4.737%	$232.8304	$232.83	$232.85	$232.80
Purchase #5	$245.83	11.667%	$274.511	$274.51	$274.50	$274.50
Purchase #6	$192.36	3.736%	$199.5466	$199.55	$199.55	$199.50
Purchase #7	$120.51	10.862%	$133.5998	$133.60	$133.60	$133.60
7 purchase totals =	$1,087.78		$1,167.9581	$1,167.96	$1,168.00	$1,167.80