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	$74.74	10.547%	$82.6228	$82.62	$82.60	$82.60
Purchase #2	$22.83	3.294%	$23.582	$23.58	$23.60	$23.60
Purchase #3	$17.96	3.652%	$18.6159	$18.62	$18.60	$18.60
Purchase #4	$153.50	6.489%	$163.4606	$163.46	$163.45	$163.50
Purchase #5	$116.25	12.495%	$130.7754	$130.78	$130.80	$130.80
Purchase #6	$7.30	8.524%	$7.9223	$7.92	$7.90	$7.90
Purchase #7	$147.43	11.607%	$164.5422	$164.54	$164.55	$164.50
7 purchase totals =	$540.01		$591.5212	$591.52	$591.50	$591.50