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	$82.90	12.699%	$93.4275	$93.43	$93.45	$93.40
Purchase #2	$159.41	3.183%	$164.484	$164.48	$164.50	$164.50
Purchase #3	$59.90	11.556%	$66.822	$66.82	$66.80	$66.80
Purchase #4	$242.31	3.282%	$250.2626	$250.26	$250.25	$250.30
Purchase #5	$95.47	12.286%	$107.1994	$107.20	$107.20	$107.20
Purchase #6	$198.38	4.114%	$206.5414	$206.54	$206.55	$206.50
Purchase #7	$54.89	7.654%	$59.0913	$59.09	$59.10	$59.10
7 purchase totals =	$893.26		$947.8282	$947.82	$947.85	$947.80