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	$93.50	8.408%	$101.3615	$101.36	$101.35	$101.40
Purchase #2	$133.87	6.110%	$142.0495	$142.05	$142.05	$142.00
Purchase #3	$38.79	4.381%	$40.4894	$40.49	$40.50	$40.50
Purchase #4	$180.47	5.635%	$190.6395	$190.64	$190.65	$190.60
Purchase #5	$89.78	11.649%	$100.2385	$100.24	$100.25	$100.20
Purchase #6	$128.84	7.335%	$138.2904	$138.29	$138.30	$138.30
Purchase #7	$113.68	5.126%	$119.5072	$119.51	$119.50	$119.50
7 purchase totals =	$778.93		$832.5760	$832.58	$832.60	$832.50