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	$42.44	3.297%	$43.8392	$43.84	$43.85	$43.80
Purchase #2	$68.85	3.851%	$71.5014	$71.50	$71.50	$71.50
Purchase #3	$249.94	11.681%	$279.1355	$279.14	$279.15	$279.10
Purchase #4	$120.38	13.117%	$136.1702	$136.17	$136.15	$136.20
Purchase #5	$198.73	8.479%	$215.5803	$215.58	$215.60	$215.60
Purchase #6	$139.64	4.658%	$146.1444	$146.14	$146.15	$146.10
Purchase #7	$36.80	6.394%	$39.153	$39.15	$39.15	$39.20
7 purchase totals =	$856.78		$931.5240	$931.52	$931.55	$931.50