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	$222.35	7.413%	$238.8328	$238.83	$238.85	$238.80
Purchase #2	$195.85	9.268%	$214.0014	$214.00	$214.00	$214.00
Purchase #3	$248.86	9.507%	$272.5191	$272.52	$272.50	$272.50
Purchase #4	$100.86	8.553%	$109.4866	$109.49	$109.50	$109.50
Purchase #5	$225.39	7.841%	$243.0628	$243.06	$243.05	$243.10
Purchase #6	$182.57	9.564%	$200.031	$200.03	$200.05	$200.00
Purchase #7	$49.69	3.688%	$51.5226	$51.52	$51.50	$51.50
7 purchase totals =	$1,225.57		$1,329.4563	$1,329.45	$1,329.45	$1,329.40