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	$228.84	4.410%	$238.9318	$238.93	$238.95	$238.90
Purchase #2	$177.29	5.338%	$186.7537	$186.75	$186.75	$186.80
Purchase #3	$33.45	11.571%	$37.3205	$37.32	$37.30	$37.30
Purchase #4	$10.85	11.160%	$12.0609	$12.06	$12.05	$12.10
Purchase #5	$100.57	12.595%	$113.2368	$113.24	$113.25	$113.20
Purchase #6	$161.54	10.581%	$178.6325	$178.63	$178.65	$178.60
Purchase #7	$97.89	6.187%	$103.9465	$103.95	$103.95	$103.90
7 purchase totals =	$810.43		$870.8827	$870.88	$870.90	$870.80