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	$151.67	8.643%	$164.7788	$164.78	$164.80	$164.80
Purchase #2	$152.32	10.808%	$168.7827	$168.78	$168.80	$168.80
Purchase #3	$140.46	4.851%	$147.2737	$147.27	$147.25	$147.30
Purchase #4	$41.85	13.766%	$47.6111	$47.61	$47.60	$47.60
Purchase #5	$128.43	10.450%	$141.8509	$141.85	$141.85	$141.90
Purchase #6	$143.48	9.787%	$157.5224	$157.52	$157.50	$157.50
Purchase #7	$228.43	8.651%	$248.1915	$248.19	$248.20	$248.20
7 purchase totals =	$986.64		$1,076.0111	$1,076.00	$1,076.00	$1,076.10