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	$138.89	8.735%	$151.022	$151.02	$151.00	$151.00
Purchase #2	$156.30	12.716%	$176.1751	$176.18	$176.20	$176.20
Purchase #3	$168.40	7.830%	$181.5857	$181.59	$181.60	$181.60
Purchase #4	$180.46	13.783%	$205.3328	$205.33	$205.35	$205.30
Purchase #5	$84.68	12.795%	$95.5148	$95.51	$95.50	$95.50
Purchase #6	$183.85	3.503%	$190.2903	$190.29	$190.30	$190.30
Purchase #7	$24.79	3.258%	$25.5977	$25.60	$25.60	$25.60
7 purchase totals =	$937.37		$1,025.5184	$1,025.52	$1,025.55	$1,025.50