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	$173.52	7.157%	$185.9388	$185.94	$185.95	$185.90
Purchase #2	$138.31	9.549%	$151.5172	$151.52	$151.50	$151.50
Purchase #3	$57.84	3.490%	$59.8586	$59.86	$59.85	$59.90
Purchase #4	$171.61	9.610%	$188.1017	$188.10	$188.10	$188.10
Purchase #5	$249.90	5.621%	$263.9469	$263.95	$263.95	$263.90
Purchase #6	$128.75	11.523%	$143.5859	$143.59	$143.60	$143.60
Purchase #7	$123.31	3.836%	$128.0402	$128.04	$128.05	$128.00
7 purchase totals =	$1,043.24		$1,120.9893	$1,121.00	$1,121.00	$1,120.90