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	$10.90	5.840%	$11.5366	$11.54	$11.55	$11.50
Purchase #2	$190.49	4.246%	$198.5782	$198.58	$198.60	$198.60
Purchase #3	$236.93	9.267%	$258.8863	$258.89	$258.90	$258.90
Purchase #4	$78.33	4.781%	$82.075	$82.08	$82.10	$82.10
Purchase #5	$120.54	5.527%	$127.2022	$127.20	$127.20	$127.20
Purchase #6	$173.49	12.680%	$195.4885	$195.49	$195.50	$195.50
Purchase #7	$224.28	6.366%	$238.5577	$238.56	$238.55	$238.60
7 purchase totals =	$1,034.96		$1,112.3245	$1,112.34	$1,112.40	$1,112.40