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	$183.46	5.124%	$192.8605	$192.86	$192.85	$192.90
Purchase #2	$52.50	13.560%	$59.619	$59.62	$59.60	$59.60
Purchase #3	$179.39	3.531%	$185.7243	$185.72	$185.70	$185.70
Purchase #4	$118.47	12.118%	$132.8262	$132.83	$132.85	$132.80
Purchase #5	$182.47	5.420%	$192.3599	$192.36	$192.35	$192.40
Purchase #6	$137.45	7.126%	$147.2447	$147.24	$147.25	$147.20
Purchase #7	$240.32	13.698%	$273.239	$273.24	$273.25	$273.20
7 purchase totals =	$1,094.06		$1,183.8736	$1,183.87	$1,183.85	$1,183.80