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	$242.89	5.551%	$256.3728	$256.37	$256.35	$256.40
Purchase #2	$126.85	9.657%	$139.0999	$139.10	$139.10	$139.10
Purchase #3	$118.44	6.664%	$126.3328	$126.33	$126.35	$126.30
Purchase #4	$115.54	3.447%	$119.5227	$119.52	$119.50	$119.50
Purchase #5	$232.68	4.793%	$243.8324	$243.83	$243.85	$243.80
Purchase #6	$94.50	6.753%	$100.8816	$100.88	$100.90	$100.90
Purchase #7	$72.91	6.206%	$77.4348	$77.43	$77.45	$77.40
7 purchase totals =	$1,003.81		$1,063.4770	$1,063.46	$1,063.50	$1,063.40