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	$95.61	10.788%	$105.9244	$105.92	$105.90	$105.90
Purchase #2	$32.95	13.617%	$37.4368	$37.44	$37.45	$37.40
Purchase #3	$100.92	11.423%	$112.4481	$112.45	$112.45	$112.40
Purchase #4	$235.43	12.670%	$265.259	$265.26	$265.25	$265.30
Purchase #5	$225.92	12.527%	$254.221	$254.22	$254.20	$254.20
Purchase #6	$185.94	5.641%	$196.4289	$196.43	$196.45	$196.40
Purchase #7	$158.65	3.532%	$164.2535	$164.25	$164.25	$164.30
7 purchase totals =	$1,035.42		$1,135.9717	$1,135.97	$1,135.95	$1,135.90