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	$219.46	11.674%	$245.0798	$245.08	$245.10	$245.10
Purchase #2	$112.77	5.742%	$119.2453	$119.25	$119.25	$119.20
Purchase #3	$122.83	4.661%	$128.5551	$128.56	$128.55	$128.60
Purchase #4	$38.46	8.109%	$41.5787	$41.58	$41.60	$41.60
Purchase #5	$172.73	4.469%	$180.4493	$180.45	$180.45	$180.40
Purchase #6	$43.47	3.819%	$45.1301	$45.13	$45.15	$45.10
Purchase #7	$100.48	6.666%	$107.178	$107.18	$107.20	$107.20
7 purchase totals =	$810.20		$867.2163	$867.23	$867.30	$867.20