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	$93.90	12.723%	$105.8469	$105.85	$105.85	$105.80
Purchase #2	$212.92	7.320%	$228.5057	$228.51	$228.50	$228.50
Purchase #3	$155.65	8.358%	$168.6592	$168.66	$168.65	$168.70
Purchase #4	$146.90	11.780%	$164.2048	$164.20	$164.20	$164.20
Purchase #5	$21.38	3.270%	$22.0791	$22.08	$22.10	$22.10
Purchase #6	$231.93	4.720%	$242.8771	$242.88	$242.90	$242.90
Purchase #7	$184.54	3.342%	$190.7073	$190.71	$190.70	$190.70
7 purchase totals =	$1,047.22		$1,122.8801	$1,122.89	$1,122.90	$1,122.90