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	$42.96	9.595%	$47.082	$47.08	$47.10	$47.10
Purchase #2	$78.79	4.545%	$82.371	$82.37	$82.35	$82.40
Purchase #3	$62.52	13.713%	$71.0934	$71.09	$71.10	$71.10
Purchase #4	$239.92	12.756%	$270.5242	$270.52	$270.50	$270.50
Purchase #5	$41.35	12.765%	$46.6283	$46.63	$46.65	$46.60
Purchase #6	$133.43	8.676%	$145.0064	$145.01	$145.00	$145.00
Purchase #7	$37.30	11.177%	$41.469	$41.47	$41.45	$41.50
7 purchase totals =	$636.27		$704.1743	$704.17	$704.15	$704.20