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	$97.84	12.105%	$109.6835	$109.68	$109.70	$109.70
Purchase #2	$184.83	8.659%	$200.8344	$200.83	$200.85	$200.80
Purchase #3	$165.94	9.360%	$181.472	$181.47	$181.45	$181.50
Purchase #4	$160.69	3.236%	$165.8899	$165.89	$165.90	$165.90
Purchase #5	$39.74	7.158%	$42.5846	$42.58	$42.60	$42.60
Purchase #6	$233.74	10.400%	$258.049	$258.05	$258.05	$258.00
Purchase #7	$231.82	12.381%	$260.5216	$260.52	$260.50	$260.50
7 purchase totals =	$1,114.60		$1,219.0350	$1,219.02	$1,219.05	$1,219.00