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	$136.83	7.462%	$147.0403	$147.04	$147.05	$147.00
Purchase #2	$163.39	13.302%	$185.1241	$185.12	$185.10	$185.10
Purchase #3	$145.73	9.513%	$159.5933	$159.59	$159.60	$159.60
Purchase #4	$238.29	8.231%	$257.9036	$257.90	$257.90	$257.90
Purchase #5	$142.72	9.426%	$156.1728	$156.17	$156.15	$156.20
Purchase #6	$136.61	6.176%	$145.047	$145.05	$145.05	$145.00
Purchase #7	$155.47	6.366%	$165.3672	$165.37	$165.35	$165.40
7 purchase totals =	$1,119.04		$1,216.2483	$1,216.24	$1,216.20	$1,216.20