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	$11.39	3.814%	$11.8244	$11.82	$11.80	$11.80
Purchase #2	$197.52	5.102%	$207.5975	$207.60	$207.60	$207.60
Purchase #3	$78.86	13.172%	$89.2474	$89.25	$89.25	$89.20
Purchase #4	$148.76	10.644%	$164.594	$164.59	$164.60	$164.60
Purchase #5	$219.26	4.497%	$229.1201	$229.12	$229.10	$229.10
Purchase #6	$27.47	6.311%	$29.2036	$29.20	$29.20	$29.20
Purchase #7	$131.45	9.781%	$144.3071	$144.31	$144.30	$144.30
7 purchase totals =	$814.71		$875.8941	$875.89	$875.85	$875.80