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	$139.54	8.307%	$151.1316	$151.13	$151.15	$151.10
Purchase #2	$58.94	5.577%	$62.2271	$62.23	$62.25	$62.20
Purchase #3	$147.70	8.590%	$160.3874	$160.39	$160.40	$160.40
Purchase #4	$242.89	4.861%	$254.6969	$254.70	$254.70	$254.70
Purchase #5	$130.60	9.308%	$142.7562	$142.76	$142.75	$142.80
Purchase #6	$54.37	12.794%	$61.3261	$61.33	$61.35	$61.30
Purchase #7	$73.72	6.603%	$78.5877	$78.59	$78.60	$78.60
7 purchase totals =	$847.76		$911.1130	$911.13	$911.20	$911.10