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	$218.41	5.536%	$230.5012	$230.50	$230.50	$230.50
Purchase #2	$111.82	3.271%	$115.4776	$115.48	$115.50	$115.50
Purchase #3	$134.37	10.593%	$148.6038	$148.60	$148.60	$148.60
Purchase #4	$41.82	4.597%	$43.7425	$43.74	$43.75	$43.70
Purchase #5	$169.61	10.143%	$186.8135	$186.81	$186.80	$186.80
Purchase #6	$230.92	5.318%	$243.2003	$243.20	$243.20	$243.20
Purchase #7	$108.38	10.329%	$119.5746	$119.57	$119.55	$119.60
7 purchase totals =	$1,015.33		$1,087.9135	$1,087.90	$1,087.90	$1,087.90