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	$164.95	13.854%	$187.8022	$187.80	$187.80	$187.80
Purchase #2	$70.71	6.724%	$75.4645	$75.46	$75.45	$75.50
Purchase #3	$74.72	4.652%	$78.196	$78.20	$78.20	$78.20
Purchase #4	$39.32	3.513%	$40.7013	$40.70	$40.70	$40.70
Purchase #5	$80.77	12.408%	$90.7919	$90.79	$90.80	$90.80
Purchase #6	$243.95	12.771%	$275.1049	$275.10	$275.10	$275.10
Purchase #7	$136.34	11.312%	$151.7628	$151.76	$151.75	$151.80
7 purchase totals =	$810.76		$899.8236	$899.81	$899.80	$899.90