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	$181.72	9.827%	$199.5776	$199.58	$199.60	$199.60
Purchase #2	$83.89	8.709%	$91.196	$91.20	$91.20	$91.20
Purchase #3	$81.51	6.238%	$86.5946	$86.59	$86.60	$86.60
Purchase #4	$90.44	3.548%	$93.6488	$93.65	$93.65	$93.60
Purchase #5	$18.41	11.666%	$20.5577	$20.56	$20.55	$20.60
Purchase #6	$93.71	13.535%	$106.3936	$106.39	$106.40	$106.40
Purchase #7	$100.46	12.429%	$112.9462	$112.95	$112.95	$112.90
7 purchase totals =	$650.14		$710.9145	$710.92	$710.95	$710.90