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	$229.84	13.135%	$260.0295	$260.03	$260.05	$260.00
Purchase #2	$17.60	10.642%	$19.473	$19.47	$19.45	$19.50
Purchase #3	$220.91	3.243%	$228.0741	$228.07	$228.05	$228.10
Purchase #4	$55.39	7.503%	$59.5459	$59.55	$59.55	$59.50
Purchase #5	$242.34	6.709%	$258.5986	$258.60	$258.60	$258.60
Purchase #6	$43.56	4.569%	$45.5503	$45.55	$45.55	$45.60
Purchase #7	$204.34	3.373%	$211.2324	$211.23	$211.25	$211.20
7 purchase totals =	$1,013.98		$1,082.5038	$1,082.50	$1,082.50	$1,082.50