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	$155.84	11.640%	$173.9798	$173.98	$174.00	$174.00
Purchase #2	$234.30	9.825%	$257.32	$257.32	$257.30	$257.30
Purchase #3	$122.82	13.588%	$139.5088	$139.51	$139.50	$139.50
Purchase #4	$95.66	6.462%	$101.8415	$101.84	$101.85	$101.80
Purchase #5	$124.98	12.848%	$141.0374	$141.04	$141.05	$141.00
Purchase #6	$63.69	3.284%	$65.7816	$65.78	$65.80	$65.80
Purchase #7	$209.67	6.140%	$222.5437	$222.54	$222.55	$222.50
7 purchase totals =	$1,006.96		$1,102.0128	$1,102.01	$1,102.05	$1,101.90