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	$183.51	4.209%	$191.2339	$191.23	$191.25	$191.20
Purchase #2	$83.90	4.166%	$87.3953	$87.40	$87.40	$87.40
Purchase #3	$212.41	13.630%	$241.3615	$241.36	$241.35	$241.40
Purchase #4	$69.53	13.282%	$78.765	$78.77	$78.75	$78.80
Purchase #5	$241.83	10.586%	$267.4301	$267.43	$267.45	$267.40
Purchase #6	$74.44	11.248%	$82.813	$82.81	$82.80	$82.80
Purchase #7	$149.67	13.131%	$169.3232	$169.32	$169.30	$169.30
7 purchase totals =	$1,015.29		$1,118.3220	$1,118.32	$1,118.30	$1,118.30