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	$229.49	8.491%	$248.976	$248.98	$249.00	$249.00
Purchase #2	$240.28	4.429%	$250.922	$250.92	$250.90	$250.90
Purchase #3	$37.96	13.617%	$43.129	$43.13	$43.15	$43.10
Purchase #4	$89.63	6.724%	$95.6567	$95.66	$95.65	$95.70
Purchase #5	$219.30	6.326%	$233.1729	$233.17	$233.15	$233.20
Purchase #6	$41.90	4.758%	$43.8936	$43.89	$43.90	$43.90
Purchase #7	$40.42	11.786%	$45.1839	$45.18	$45.20	$45.20
7 purchase totals =	$898.98		$960.9341	$960.93	$960.95	$961.00