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	$156.72	12.488%	$176.2912	$176.29	$176.30	$176.30
Purchase #2	$126.37	4.661%	$132.2601	$132.26	$132.25	$132.30
Purchase #3	$128.27	13.441%	$145.5108	$145.51	$145.50	$145.50
Purchase #4	$137.63	13.558%	$156.2899	$156.29	$156.30	$156.30
Purchase #5	$226.40	10.470%	$250.1041	$250.10	$250.10	$250.10
Purchase #6	$111.76	4.573%	$116.8708	$116.87	$116.85	$116.90
Purchase #7	$87.76	12.452%	$98.6879	$98.69	$98.70	$98.70
7 purchase totals =	$974.91		$1,076.0148	$1,076.01	$1,076.00	$1,076.10