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	$158.48	11.442%	$176.6133	$176.61	$176.60	$176.60
Purchase #2	$160.83	9.556%	$176.1989	$176.20	$176.20	$176.20
Purchase #3	$144.50	4.865%	$151.5299	$151.53	$151.55	$151.50
Purchase #4	$46.56	13.473%	$52.833	$52.83	$52.85	$52.80
Purchase #5	$176.33	5.320%	$185.7108	$185.71	$185.70	$185.70
Purchase #6	$146.52	11.133%	$162.8321	$162.83	$162.85	$162.80
Purchase #7	$111.57	10.550%	$123.3406	$123.34	$123.35	$123.30
7 purchase totals =	$944.79		$1,029.0586	$1,029.05	$1,029.10	$1,028.90