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	$179.38	11.233%	$199.5298	$199.53	$199.55	$199.50
Purchase #2	$78.34	5.798%	$82.8822	$82.88	$82.90	$82.90
Purchase #3	$168.71	13.181%	$190.9477	$190.95	$190.95	$190.90
Purchase #4	$235.34	6.196%	$249.9217	$249.92	$249.90	$249.90
Purchase #5	$149.28	12.702%	$168.2415	$168.24	$168.25	$168.20
Purchase #6	$66.88	4.139%	$69.6482	$69.65	$69.65	$69.60
Purchase #7	$97.30	8.226%	$105.3039	$105.30	$105.30	$105.30
7 purchase totals =	$975.23		$1,066.4750	$1,066.47	$1,066.50	$1,066.30