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	$182.81	6.568%	$194.817	$194.82	$194.80	$194.80
Purchase #2	$156.96	12.390%	$176.4073	$176.41	$176.40	$176.40
Purchase #3	$164.49	10.439%	$181.6611	$181.66	$181.65	$181.70
Purchase #4	$54.79	9.407%	$59.9441	$59.94	$59.95	$59.90
Purchase #5	$24.66	9.714%	$27.0555	$27.06	$27.05	$27.10
Purchase #6	$142.44	11.531%	$158.8648	$158.86	$158.85	$158.90
Purchase #7	$189.46	12.330%	$212.8204	$212.82	$212.80	$212.80
7 purchase totals =	$915.61		$1,011.5702	$1,011.57	$1,011.50	$1,011.60