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	$110.69	11.860%	$123.8178	$123.82	$123.80	$123.80
Purchase #2	$46.32	13.249%	$52.4569	$52.46	$52.45	$52.50
Purchase #3	$187.32	6.243%	$199.0144	$199.01	$199.00	$199.00
Purchase #4	$204.77	13.570%	$232.5573	$232.56	$232.55	$232.60
Purchase #5	$203.94	13.609%	$231.6942	$231.69	$231.70	$231.70
Purchase #6	$241.35	7.430%	$259.2823	$259.28	$259.30	$259.30
Purchase #7	$55.92	10.537%	$61.8123	$61.81	$61.80	$61.80
7 purchase totals =	$1,050.31		$1,160.6352	$1,160.63	$1,160.60	$1,160.70