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	$133.89	6.267%	$142.2809	$142.28	$142.30	$142.30
Purchase #2	$204.95	3.774%	$212.6848	$212.68	$212.70	$212.70
Purchase #3	$183.95	11.455%	$205.0215	$205.02	$205.00	$205.00
Purchase #4	$230.78	9.735%	$253.2464	$253.25	$253.25	$253.20
Purchase #5	$83.78	13.189%	$94.8297	$94.83	$94.85	$94.80
Purchase #6	$69.64	4.387%	$72.6951	$72.70	$72.70	$72.70
Purchase #7	$155.96	8.561%	$169.3117	$169.31	$169.30	$169.30
7 purchase totals =	$1,062.95		$1,150.0701	$1,150.07	$1,150.10	$1,150.00