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	$179.29	6.703%	$191.3078	$191.31	$191.30	$191.30
Purchase #2	$216.93	6.643%	$231.3407	$231.34	$231.35	$231.30
Purchase #3	$34.55	10.596%	$38.2109	$38.21	$38.20	$38.20
Purchase #4	$221.59	7.726%	$238.71	$238.71	$238.70	$238.70
Purchase #5	$127.83	9.832%	$140.3982	$140.40	$140.40	$140.40
Purchase #6	$189.82	8.365%	$205.6984	$205.70	$205.70	$205.70
Purchase #7	$139.31	8.436%	$151.0622	$151.06	$151.05	$151.10
7 purchase totals =	$1,109.32		$1,196.7282	$1,196.73	$1,196.70	$1,196.70