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	$150.95	7.348%	$162.0418	$162.04	$162.05	$162.00
Purchase #2	$198.41	7.399%	$213.0904	$213.09	$213.10	$213.10
Purchase #3	$116.64	13.105%	$131.9257	$131.93	$131.95	$131.90
Purchase #4	$223.75	4.410%	$233.6174	$233.62	$233.60	$233.60
Purchase #5	$40.66	4.515%	$42.4958	$42.50	$42.50	$42.50
Purchase #6	$145.70	13.722%	$165.693	$165.69	$165.70	$165.70
Purchase #7	$20.90	10.113%	$23.0136	$23.01	$23.00	$23.00
7 purchase totals =	$897.01		$971.8777	$971.88	$971.90	$971.80